Short chain alcohol production from glycerin

ABSTRACT

A method of producing short chain alcohols from glycerol generated as a byproduct of biodiesel production is provided utilizing separate dehydration and hydrogenation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 60/930,704, filed on May 18, 2007 and U.S.Provisional Application No. 61/023,816, filed on Jan. 25, 2008; thedisclosures of each of which are hereby expressly incorporated byreference in their entireties and are hereby expressly made a portion ofthis application.

FIELD OF THE INVENTION

A method of producing short chain alcohols from glycerol generated as abyproduct of biodiesel production is provided.

BACKGROUND OF THE INVENTION

Biodiesel is a fuel derived from vegetable oils or animal fats. In use,it has similar properties as conventional (petroleum-based) diesel fuel.A common form of biodiesel includes the methyl ester or ethyl ester offatty acids obtained from vegetable oil or animal fat. Vegetable oilsand animal fats are generally triglycerides. Biodiesel is usuallyproduced either by the direct esterification of fatty acids or by thetransesterification of the source oil.

Glycerol is a byproduct of the production of fatty acids and of thetransesterification process used to produce biodiesel. Depending on theparticular fat or oil used as the biodiesel source, glycerol as abyproduct can comprise up to approximately 9-11 wt. % of the startingmaterial.

Several markets already exist for glycerol as a byproduct of fatty acidor biodiesel production. Glycerol is a common feedstock in the synthesisof various chemicals, and has a number of uses in pharmaceuticalformulations. However, these markets typically require highly purifiedglycerol. Such purification can be costly and must be done in alarge-scale operation to be profitable. In addition, as the volume ofbiodiesel production (and thus byproduct glycerol production) increases,existing markets for glycerol are becoming saturated and the price paidfor the glycerol will decrease, adversely impacting the economics ofbiodiesel production.

In addition, the need to supply raw material monohydric alcohols to abiodiesel production facility, and the simultaneous need to ship outside product glycerol from the facility can increase the cost for thebiodiesel produced and can limit the facility siting geographically tothose locations with good and inexpensive transport as well as proximityto markets for the glycerol and supplies for the alcohols. Further,because the price paid for the glycerol depends on the use it is put to,acceptable facility siting can be limited even further to thoselocations readily accessible to facilities that will pay a premium forthe glycerol, such as pharmaceutical, cosmetic, and personal carefacilities.

In addition, the transport itself of the alcohols and the glycerol is anundesirable aspect of many proposed biodiesel facilities. Such transportincreases the consumption of motor fuels which increases air pollutionand can lead to other environmental problems. Use of the glycerol onsite as a valuable material can reduce these unfortunate problems withconventional biodiesel operations.

Finally, the need to supply monohydric alcohol from outside sources to abiodiesel facility means that other resources will be needed to supportthe biodiesel production at that facility. If instead, this raw materialcan be produced on-site from materials that are readily available at thelocation, fewer outside resources will be needed to support the facilityand resulting in a smaller environmental footprint for the facility.

SUMMARY OF THE INVENTION

An economically viable use for glycerol produced as a byproduct ofbiodiesel production is highly desirable. A method is provided forconverting glycerol to monohydric alcohols, which are a valuablefeedstock in the production of biodiesel.

Accordingly, in a first aspect a method is provided for producing amonohydric alcohol from glycerol, the method comprising reacting a gasphase mixture comprising glycerol and hydrogen in a presence of aheterogeneous catalyst system to yield a reaction mixture comprising atleast one carbonyl compound, wherein the heterogeneous catalyst systemcomprises a dehydration catalyst and a hydrogenation catalyst, andwherein conditions of the dehydration reaction and conditions of thehydrogenation reaction are controlled such that a heat required by thedehydration reaction balances a heat generated by the hydrogenationreaction; and reacting a mixture comprising hydrogen and at least aportion of the reaction mixture comprising at least one carbonylcompound over a hydrogenation catalyst to yield a reaction streamcomprising at least one monohydric alcohol.

In an embodiment of the first aspect, an absolute value of the heatrequired by the dehydration reaction is provided by an absolute value ofthe heat generated by the hydrogenation reaction.

In an embodiment of the first aspect, an absolute value of the heatgenerated by the hydrogenation reaction provides an absolute value ofthe heat required by the dehydration reaction and additional heat forother processes.

In an embodiment of the first aspect, the heterogeneous catalyst systemcomprises a first portion and a second portion, the first portioncomprising a mixture of dehydration catalyst and hydrogenation catalyst,wherein the hydrogenation catalyst and the dehydration catalyst aredifferent from each other.

In an embodiment of the first aspect, the heterogeneous catalyst systemcomprises a first portion and a second portion, the first portion has afirst dehydration activity and a first hydrogenation activity andcomprises a mixture of dehydration catalyst and hydrogenation catalyst,wherein the hydrogenation catalyst and the dehydration catalyst aredifferent from each other; the second portion of the heterogeneouscatalyst system has a second dehydration activity and a secondhydrogenation activity, and wherein a ratio of the first hydrogenationactivity to the first dehydration activity is less than a ratio of thesecond hydrogenation activity to the second dehydration activity.

In an embodiment of the first aspect, the heterogeneous catalyst systemcomprises a first portion and a second portion, the first portion has afirst dehydration activity and a first hydrogenation activity andcomprises a mixture of dehydration catalyst and hydrogenation catalyst,wherein the hydrogenation catalyst and the dehydration catalyst aredifferent from each other; the second portion of the heterogeneouscatalyst system has a second dehydration activity and a secondhydrogenation activity, and wherein a ratio of the first hydrogenationactivity to the first dehydration activity is less than a ratio of thesecond hydrogenation activity to the second dehydration activity and aratio of the first hydrogenation activity to the second hydrogenationactivity is from about 0:1 to about 1:5.

In an embodiment of the first aspect, the heterogeneous catalyst systemcomprises a first portion and a second portion, the first portion has afirst dehydration activity and a first hydrogenation activity andcomprises a mixture of dehydration catalyst and hydrogenation catalyst,wherein the hydrogenation catalyst and the dehydration catalyst aredifferent from each other; the second portion of the heterogeneouscatalyst system has a second dehydration activity and a secondhydrogenation activity, and wherein a ratio of the first hydrogenationactivity to the first dehydration activity is less than a ratio of thesecond hydrogenation activity to the second dehydration activity, and aratio of the first hydrogenation activity to the first dehydrationactivity is from about 0:1 to about 1:5.

In an embodiment of the first aspect, the heterogeneous catalyst systemcomprises a first portion and a second portion, the first portion has afirst dehydration activity and a first hydrogenation activity andcomprises a mixture of dehydration catalyst and hydrogenation catalyst,wherein the hydrogenation catalyst and the dehydration catalyst aredifferent from each other; the second portion of the heterogeneouscatalyst system has a second dehydration activity and a secondhydrogenation activity, and wherein a ratio of the first hydrogenationactivity to the first dehydration activity is less than a ratio of thesecond hydrogenation activity to the second dehydration activity;wherein the gas phase mixture comprising glycerol and hydrogen isexposed to the first portion to produce an intermediate stream, and theintermediate stream is exposed to the second portion.

In an embodiment of the first aspect, the heat required by thedehydration reaction and the heat generated by the hydrogenationreaction are balanced by controlling a ratio of an amount of dehydrationcatalyst to an amount of hydrogenation catalyst in the heterogeneouscatalyst system.

In an embodiment of the first aspect, a molar ratio of hydrogen toglycerol in the gas phase mixture is from about 0.05:10 to about 2:1.

In an embodiment of the first aspect, a molar ratio of hydrogen toglycerol in the gas phase mixture is from about 0.1:10 to about 3:2.

In an embodiment of the first aspect, the heat required by thedehydration reaction and the heat generated by the hydrogenationreaction are balanced by controlling a ratio of hydrogen to glycerol.

In an embodiment of the first aspect, an amount of hydrogen in themixture comprising hydrogen and at least a portion the carbonyl compoundis such that hydrogen is present in excess of a stoichiometric amountnecessary for conversion of all carbonyl groups present in the mixtureto hydroxyl groups.

In an embodiment of the first aspect, an amount of hydrogen in themixture comprising hydrogen and at least a portion the carbonyl compoundis such that hydrogen is present at least 10% in excess of astoichiometric amount necessary for conversion of all carbonyl groupspresent in the mixture to hydroxyl groups.

In an embodiment of the first aspect, an amount of hydrogen in themixture comprising hydrogen and at least a portion the carbonyl compoundis such that hydrogen is present at least 20% in excess of astoichiometric amount necessary for conversion of all carbonyl groupspresent in the mixture to hydroxyl groups.

In an embodiment of the first aspect, an amount of hydrogen in themixture comprising hydrogen and at least a portion the carbonyl compoundis such that hydrogen is present at least 30% in excess of astoichiometric amount necessary for conversion of all carbonyl groupspresent in the mixture to hydroxyl groups.

In an embodiment of the first aspect, an amount of hydrogen in themixture comprising hydrogen and at least a portion the carbonyl compoundis such that hydrogen is present from about 40% to about 150% in excessof a stoichiometric amount necessary for conversion of all carbonylgroups present in the mixture to hydroxyl groups.

In an embodiment of the first aspect, the gas phase mixture comprisingglycerol and hydrogen further comprises water.

In an embodiment of the first aspect, the gas phase mixture comprisingglycerol and hydrogen further comprises water, and the water andglycerol are present in the gas phase mixture in a weight ratio of fromabout 3:1 to about 9:1.

In an embodiment of the first aspect, the gas phase mixture comprisingglycerol and hydrogen further comprises water, and the water andglycerol are present in the gas phase mixture in a weight ratio of fromabout 4:1 to about 6:1.

In an embodiment of the first aspect, the gas phase mixture comprisingglycerol and hydrogen further comprises water, and the water comprisesfrom about 60 wt. % to about 90 wt. % of the gas phase mixture.

In an embodiment of the first aspect, the gas phase mixture comprisingglycerol and hydrogen further comprises water, and the water comprisesfrom about 70 wt. % to about 90 wt. % of the gas phase mixture.

In an embodiment of the first aspect, glycerol comprises from about 10wt. % to about 40 wt. % wt. of the gas phase mixture.

In an embodiment of the first aspect, glycerol comprises from about 15wt. % to about 25 wt. % wt. of the gas phase mixture.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and at apressure of from about 0.5 bar to about 10 bar, and the reaction streamcomprises a mixture of ethanol, methanol, and propanol.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about60% of the total mass of monohydric alcohols in the reaction stream.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up about 70% toabout 100% of the total mass of monohydric alcohols in the reactionstream.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up about 80% toabout 100% of the total mass of monohydric alcohols in the reactionstream.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream; andwater is removed from the reaction mixture comprising at least onecarbonyl compound prior to reacting hydrogen and at least a portion ofthe reaction mixture over the hydrogenation catalyst.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream; andfrom about 10% to about 100% of the water present in the reactionmixture comprising at least one carbonyl compound is removed prior toreacting hydrogen and at least a portion of the reaction mixture overthe hydrogenation catalyst.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream; andfrom about 50% to about 90% of the water present in the reaction mixturecomprising at least one carbonyl compound is removed prior to reactinghydrogen and at least a portion of the reaction mixture over thehydrogenation catalyst.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream; andfrom about 60% to about 80% of the water present in the reaction mixturecomprising at least one carbonyl compound is removed prior to reactinghydrogen and at least a portion of the reaction mixture over thehydrogenation catalyst.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream; thereaction mixture comprising at least one carbonyl compound comprises atleast one aldehyde; water is removed from the reaction mixturecomprising at least one carbonyl compound prior to reacting hydrogen andat least a portion of the reaction mixture over the hydrogenationcatalyst; and a weight ratio water to aldehyde present after removingwater is from about 20:80 to about 1:99.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream; thereaction mixture comprising at least one carbonyl compound comprises atleast one aldehyde; water is removed from the reaction mixturecomprising at least one carbonyl compound prior to reacting hydrogen andat least a portion of the reaction mixture over the hydrogenationcatalyst; and a weight ratio water to aldehyde present after removingwater is from about 10:90 to about 1:99.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream; thereaction mixture comprising at least one carbonyl compound comprises atleast one aldehyde which is propionaldehyde; water is removed from thereaction mixture comprising at least one carbonyl compound prior toreacting hydrogen and at least a portion of the reaction mixture overthe hydrogenation catalyst; and a weight ratio water to propionaldehydepresent after removing water is from about 10:90 to about 1:99.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream; thereaction mixture comprising at least one carbonyl compound comprises atleast one aldehyde which is propionaldehyde, and the propionaldehydemakes up from about 80 wt. % to about 100 wt. % of the aldehydes presentin the reaction mixture comprising at least one carbonyl compound; wateris removed from the reaction mixture comprising at least one carbonylcompound prior to reacting hydrogen and at least a portion of thereaction mixture over the hydrogenation catalyst; and a weight ratiowater to propionaldehyde present after removing water is from about10:90 to about 1:99.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up from about 70wt. % to about 100 wt. % of the monohydric alcohols present in thereaction stream; and water is removed from the reaction mixturecomprising at least one carbonyl compound prior to reacting hydrogen andat least a portion of the reaction mixture over the hydrogenationcatalyst.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream;water is removed from the reaction mixture comprising at least onecarbonyl compound prior to reacting hydrogen and at least a portion ofthe reaction mixture over the hydrogenation catalyst; and a weight ratioof water to glycerol in the gas phase mixture comprising glycerol andhydrogen is from about 4:1 to about 8:1.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 280° C. to about 320° C. and a pressureof about 5 bar to about 7 bar, and propanol makes up more than about 50%of the total mass of monohydric alcohols in the reaction stream; wateris removed from the reaction mixture comprising at least one carbonylcompound prior to reacting hydrogen and at least a portion of thereaction mixture over the hydrogenation catalyst; and a weight ratio ofwater to glycerol in the gas phase mixture comprising glycerol andhydrogen is from about 4:1 to about 8:1

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream;water is removed from the reaction mixture comprising at least onecarbonyl compound prior to reacting hydrogen and at least a portion ofthe reaction mixture over the hydrogenation catalyst; and a partialpressure of glycerol in the gas phase mixture comprising glycerol andhydrogen is from about 40 mbar to about 400 mbar.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream; andwater is removed from the reaction mixture comprising at least onecarbonyl compound prior to reacting hydrogen and at least a portion ofthe reaction mixture over the hydrogenation catalyst; and the reactionstream comprising monohydric alcohol comprises less than about 10 wt. %water.

In an embodiment of the first aspect, the gas phase mixture is reactedat a temperature of from about 260° C. to about 340° C. and a pressureof about 0.5 bar to about 10 bar, and propanol makes up more than about50% of the total mass of monohydric alcohols in the reaction stream; andwater is removed from the reaction mixture comprising at least onecarbonyl compound prior to reacting hydrogen and at least a portion ofthe reaction mixture over the hydrogenation catalyst; and the reactionstream comprising monohydric alcohol comprises less than about 5 wt. %water.

In an embodiment of the first aspect, the reaction mixture comprising atleast one carbonyl compound comprises acrolein and propionaldehydepresent in a weight ratio of from about 6:1 to about 0:10.

In an embodiment of the first aspect, wherein the reaction mixturecomprising at least one carbonyl compound comprises acrolein andpropionaldehyde present in a weight ratio of from about 1:1 to about0:10.

In an embodiment of the first aspect, the heterogeneous catalyst systemfurther comprises a reforming catalyst.

In an embodiment of the first aspect, the heterogeneous catalyst systemfurther comprises a reforming catalyst, and the first reacted mixturecomprises acrolein and propionaldehyde present in a weight ratio of fromabout 6:1 to about 0:10.

In an embodiment of the first aspect, the heterogeneous catalyst systemfurther comprises a reforming catalyst, and the first reacted mixturecomprises propanol and propionaldehyde present in a weight ratio of fromabout 0:10 to about 2:8.

In an embodiment of the first aspect, the heterogeneous catalyst systemfurther comprises a reforming catalyst, the reaction mixture comprisingat least one carbonyl compound comprises acrolein and propionaldehydepresent in a weight ratio of from about 6:1 to about 0:10, and more thanabout 50% of the hydrogen is from reforming of the gas mixture.

In a second aspect, a method is provided for converting glycerol tomonohydric alcohol, the method comprising reacting a gaseous mixturecomprising glycerol and water in a first reaction bed comprising aheterogeneous catalyst system comprising a dehydration catalyst and ahydrogenation catalyst, whereby a first reacted mixture is produced;separating at least a portion of the first reacted mixture into a morevolatile fraction and a less volatile fraction in a first condenser;reacting a mixture of hydrogen and at least a portion of the morevolatile fraction from the first reacted mixture in a second reactor bedcomprising a hydrogenation catalyst, whereby a second reacted mixturecomprising a monohydric alcohol is produced; separating at least aportion of the second reacted mixture into a less volatile fractioncomprising a monohydric alcohol and a more volatile fraction in a secondcondenser;

In an embodiment of the second aspect, a method is provided forconverting glycerol to monohydric alcohol, the method comprisingreacting a gaseous mixture comprising glycerol and water in a firstreaction bed comprising a heterogeneous catalyst system comprising adehydration catalyst and a hydrogenation catalyst, whereby a firstreacted mixture is produced; separating at least a portion of the firstreacted mixture into a more volatile fraction and a less volatilefraction in a first condenser; reacting a mixture of hydrogen and atleast a portion of the more volatile fraction from the first reactedmixture in a second reactor bed comprising a hydrogenation catalyst,whereby a second reacted mixture comprising a monohydric alcohol isproduced; separating at least a portion of the second reacted mixtureinto a less volatile fraction comprising a monohydric alcohol and a morevolatile fraction in a second condenser; and separating at least aportion of the more volatile fraction of the second reacted mixture intoa less volatile fraction comprising at least one of an aldehyde and aketone and a more volatile fraction in a third condenser.

In an embodiment of the second aspect, at least a portion of the lessvolatile fraction of the first reacted mixture is introduced into thefirst reaction bed.

In an embodiment of the second aspect, at least a portion of the lessvolatile fraction of the second reacted mixture is introduced into thesecond reaction bed.

In an embodiment of the second aspect, at least a portion of the lessvolatile fraction of the first reacted mixture is introduced into thefirst reaction bed, and at least a portion of the less volatile fractionof the first reacted mixture is volatilized prior to introducing it intothe first reaction bed.

In an embodiment of the second aspect, at least a portion of the lessvolatile fraction of the first reacted mixture is introduced into thefirst reaction bed, and at least a portion of the less volatile fractionof the first reacted mixture is volatilized prior to introducing it intothe first reaction bed, and at least a portion of the less volatilefraction of the second reacted mixture is volatilized prior tointroducing it into the second reaction bed.

In an embodiment of the second aspect, the gaseous mixture comprisingglycerol and water further comprises hydrogen.

In an embodiment of the second aspect, the gaseous mixture comprisingglycerol and water further comprises hydrogen, and the first reactionbed catalyzes dehydration reactions requiring heat and hydrogenationreactions generating heat, wherein the heat required by the dehydrationreactions approximately balances the heat generated by the hydrogenationreactions.

In an embodiment of the second aspect, the gaseous mixture comprisingglycerol and water further comprises hydrogen, and the first reactionbed catalyzes dehydration reactions requiring heat and hydrogenationreactions generating heat, wherein the heat required by the dehydrationreactions approximately balances the heat generated by the hydrogenationreactions, and an absolute value of the heat required by the dehydrationreactions is provided by an absolute value of the heat generated by thehydrogenation reactions.

In an embodiment of the second aspect, the gaseous mixture comprisingglycerol and water further comprises hydrogen, and the first reactionbed catalyzes dehydration reactions requiring heat and hydrogenationreactions generating heat, wherein the heat required by the dehydrationreactions approximately balances the heat generated by the hydrogenationreactions, and an absolute value of the heat generated by thehydrogenation reactions provides an absolute value of the heat requiredby the dehydration reactions and other processes.

In an embodiment of the second aspect, the gaseous mixture comprisingglycerol and water further comprises hydrogen, and the first reactionbed catalyzes dehydration reactions requiring heat and hydrogenationreactions generating heat, wherein the heat required by the dehydrationreactions approximately balances the heat generated by the hydrogenationreactions, and the heat required by the dehydration reactions and theheat generated by the hydrogenation reaction are balanced by controllinga ratio of an amount of dehydration catalyst to hydrogenation catalystin the first reaction bed.

In an embodiment of the second aspect, the gaseous mixture comprisingglycerol and water further comprises hydrogen, and the first reactionbed catalyzes dehydration reactions requiring heat and hydrogenationreactions generating heat, wherein the heat required by the dehydrationreactions approximately balances the heat generated by the hydrogenationreactions, and the heat required by the dehydration reactions and theheat generated by the hydrogenation reactions are balanced bycontrolling an amount of hydrogen present in the gaseous mixture.

In an embodiment of the second aspect, the gaseous mixture comprisingglycerol and water further comprises hydrogen, and the first reactionbed catalyzes dehydration reactions requiring heat and hydrogenationreactions generating heat, wherein the heat required by the dehydrationreactions approximately balances the heat generated by the hydrogenationreactions, and the heat required by the dehydration reactions and theheat generated by the hydrogenation reactions are balanced bycontrolling a ratio of hydrogen to glycerol.

In an embodiment of the second aspect, the gaseous mixture comprisingglycerol and water further comprises hydrogen, and the first reactionbed catalyzes dehydration reactions requiring heat and hydrogenationreactions generating heat, wherein the heat required by the dehydrationreactions approximately balances the heat generated by the hydrogenationreactions, the heat required by the dehydration reactions and the heatgenerated by the hydrogenation reactions are balanced by controlling anamount of hydrogen present in the gaseous mixture, and a molar ratio ofhydrogen to glycerol in the gaseous mixture is from about 0.05:10 toabout 10:10.

In an embodiment of the second aspect, the gaseous mixture comprisingglycerol and water further comprises hydrogen, and the first reactionbed catalyzes dehydration reactions requiring heat and hydrogenationreactions generating heat, wherein the heat required by the dehydrationreactions approximately balances the heat generated by the hydrogenationreactions, the heat required by the dehydration reactions and the heatgenerated by the hydrogenation reactions are balanced by controlling anamount of hydrogen present in the gaseous mixture, and a molar ratio ofhydrogen to glycerol in the gaseous mixture is from about 0.1:10 toabout 2:10.

In an embodiment of the second aspect, the heterogeneous catalyst systemhas a selectivity for conversion of glycerol to acrolein, theselectivity being greater than about 75 (wt.) %.

In an embodiment of the second aspect, the heterogeneous catalyst systemhas a selectivity for conversion of glycerol to acrolein, theselectivity being greater than about 85 (wt.) %.

In an embodiment of the second aspect, the heterogeneous catalyst systemhas a selectivity for conversion of glycerol to acrolein, theselectivity being dependent on the catalysts present, the time for thereaction, the temperature of the reaction, and the pressure of thereaction, the selectivity being greater than about 95 (wt.) %.

In an embodiment of the second aspect, the heterogeneous catalyst systemhas a selectivity for conversion of acrolein to propionaldehyde, theselectivity being greater than about 65 (wt.) %.

In an embodiment of the second aspect, the heterogeneous catalyst systemhas a selectivity for conversion of acrolein to propionaldehyde, theselectivity being greater than about 75 (wt.) %.

In an embodiment of the second aspect, the heterogeneous catalyst systemhas a selectivity for conversion of acrolein to propionaldehyde, theselectivity being greater than about 85 (wt.) %.

In an embodiment of the second aspect, the heterogeneous catalyst systemhas a selectivity for conversion of propionaldehyde to propanol, theselectivity being less than about 25 (wt.) %.

In an embodiment of the second aspect, the heterogeneous catalyst systemhas a selectivity for conversion of propionaldehyde to propanol, theselectivity being less than about 15 (wt.) %.

In an embodiment of the second aspect, the heterogeneous catalyst systemhas a selectivity for conversion of propionaldehyde to propanol, theselectivity being less than about 5 (wt.) %.

In an embodiment of the second aspect, the first reacted mixturecomprising at least one carbonyl contains less than about 10 mol % of amonohydric alcohol.

In an embodiment of the second aspect, the first reacted mixturecomprising at least one carbonyl contains less than about 3 mol % of amonohydric alcohol.

In an embodiment of the second aspect, the first reacted mixturecomprising at least one carbonyl compound comprises monohydric alcoholand propionaldehyde present in a weight ratio of from about 0:10 toabout 3:7.

In an embodiment of the second aspect, the first reacted mixturecomprising at least one carbonyl compound comprises monohydric alcoholand propionaldehyde present in a weight ratio of from about 0.1:10 toabout 1:9.

In an embodiment of the second aspect, the first reaction bed furthercomprises a reforming catalyst.

In an embodiment of the second aspect, the first reaction bed furthercomprises a reforming catalyst, and the first reacted mixture comprisesacrolein and propionaldehyde present in a weight ratio of from about 6:1to about 0:10.

In an embodiment of the second aspect, and the first reaction bedfurther comprises a reforming catalyst, the first reacted mixturecomprises propanol and propionaldehyde present in a weight ratio of fromabout 0:10 to about 2:8.

In an embodiment of the second aspect, the first reaction bed furthercomprises a reforming catalyst, the first reacted mixture comprising atleast one carbonyl compound comprises monohydric alcohol andpropionaldehyde present in a weight ratio of from about 0:10 to about3:7, and more than about 50% of the hydrogen is from reforming of thegas mixture.

In a third aspect, a method is provided for converting glycerol tomonohydric alcohol, the method comprising contacting a gaseous materialcomprising glycerol with a heterogeneous dehydration catalyst at atemperature and a pressure sufficient to convert at least a portion ofthe glycerol to one or more compounds having at least one of acarbon-carbon double bond and a carbon-oxygen double bond, whereby adehydrated glycerol material is obtained; adding hydrogen gas to thedehydrated glycerol material; contacting the mixture of hydrogen gas anddehydrated glycerol material with a hydrogenation catalyst at atemperature and a pressure sufficient to convert at least a portion ofthe compounds having at least one of a carbon-carbon double bond and acarbon-oxygen double bond to one or more monohydric alcohols, whereby ahydrogenated mixture is obtained; and separating a monohydricalcohol-rich portion from the hydrogenated mixture.

In an embodiment of the third aspect, the monohydric alcohol-richportion comprises at least 75 wt. % monohydric alcohols.

In an embodiment of the third aspect, the monohydric alcohol-richportion comprises at least 70 wt. % 1-propanol.

In an embodiment of the third aspect, wherein the step of contacting agaseous material is conducted at a pressure of from about 0.5 bar(absolute) to about 10 bar (absolute), and at a temperature of fromabout 260° C. to about 340° C.

In an embodiment of the third aspect, the step of contacting a gaseousmaterial is conducted at a pressure of from about 4 bar (absolute) toabout 7 bar (absolute), and at a temperature of from about 280° C. toabout 320° C.

In an embodiment of the third aspect, the step of contacting the mixtureof hydrogen gas and dehydrated glycerol material is conducted at apressure of from about 0.5 bar (absolute) to about 10 bar (absolute),and at a temperature of from about 150° C. to about 400° C.

In an embodiment of the third aspect, the step of contacting the mixtureof hydrogen gas and dehydrated glycerol material is conducted at apressure of from about 4 bar (absolute) to about 7 bar (absolute), andat a temperature of from about 250° C. to about 350° C.

In an embodiment of the third aspect, the dehydration catalyst comprisesoxides of tungsten and zirconium.

In an embodiment of the third aspect, the hydrogenation catalystcomprises a platinum group metal.

In an embodiment of the third aspect, an amount of hydrogen in themixture of hydrogen gas and dehydrated glycerol material is from about0.9 to about 10 times the amount of carbon-carbon double bonds andcarbon-oxygen double bonds present in the mixture on a molar basis.

In an embodiment of the third aspect, at least a portion of one compoundselected from the group glycerol, propylene glycol, ethylene glycol,hydroxyacetone, propionaldehyde, acrolein, acetone, acetaldehyde, andformaldehyde is separated from the dehydrated glycerol material; and theseparated portion is contacted with the heterogeneous dehydrationcatalyst.

In an embodiment of the third aspect, glycerol is present at a molefraction of from about 10% to about 30%, and water is present at a molefraction of from about 70% to about 90% in the gaseous material.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one monohydric alcohol.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one monohydric alcohol, and the monohydric alcohol isselected from the group consisting of methanol, ethanol, and propanol.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one monohydric alcohol, and monohydric alcohols makeup from about 0.1 wt. % to about 30 wt. % of the gaseous material.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one monohydric alcohol, and monohydric alcohols makeup from about 0.1 wt. % to about 15 wt. % of the gaseous material.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one monohydric alcohol, and monohydric alcohols makeup from about 0.1 wt. % to about 5 wt. % of the gaseous material.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one monohydric alcohol, and monohydric alcohols makeup from about 0.1 wt. % to about 2 wt. % of the gaseous material.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one monohydric alcohol, and monohydric alcohols makeup less than about 0.5 wt. % of the gaseous material.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one fatty acid methyl ester.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one fatty acid methyl ester, and fatty acid methylesters make up from about 0.1 wt. % to about 2 wt. % of the gaseousmaterial.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one fatty acid ethyl ester.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one fatty acid ethyl ester, and fatty acid ethylesters make up from about 0.1 wt. % to about 2 wt. % of the gaseousmaterial.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one fatty acid propyl ester.

In an embodiment of the third aspect, the gaseous material furthercomprises at least one fatty acid propyl ester, and fatty acid propylesters make up from about 0.1 wt. % to about 2 wt. % of the gaseousmaterial.

In an embodiment of the third aspect, the gaseous material contains fromabout 0.1 wt. % to about 20 wt. % hydrogen.

In an embodiment of the third aspect, the gaseous material furthercomprises hydrogen at about 0.2% to about 2% (molar).

In a fourth aspect, a method is provided for converting glycerol tomonohydric alcohol, the method comprising contacting a gaseous materialcomprising glycerol with a heterogeneous dehydration catalyst at atemperature and a pressure sufficient to yield a first reacted materialcomprising carbon monoxide, water, and one or more carbonyl-containingmolecules; contacting the first reacted material with a water-gas shiftreaction catalyst at a temperature and a pressure sufficient to yield asecond reacted material comprising hydrogen; and contacting the secondreacted material with a heterogeneous hydrogenation catalyst at atemperature and a pressure sufficient to convert at least a portion ofthe carbonyl-containing molecules to one or more monohydric alcohols ina hydrogenated material.

In an embodiment of the fourth aspect, the step of contacting a gaseousmixture occurs at a temperature of from about 250° C. to about 380° C.,and at a pressure of from about 1 bar (absolute) to about 10 bar(absolute).

In an embodiment of the fourth aspect, the step of contacting a gaseousmixture occurs at a temperature of from about 280° C. to about 320° C.,and a pressure of from about 4 bar (absolute) to about 7 bar (absolute).

In an embodiment of the fourth aspect, the heterogeneous dehydrationcatalyst comprises oxides of tungsten and oxides of zirconium.

In an embodiment of the fourth aspect, the step of contacting the firstreacted material is conducted at a temperature of from about 220° C. toabout 380° C., and at a pressure of from about 1 bar (absolute) to about10 bar (absolute).

In an embodiment of the fourth aspect, the step of contacting the firstreacted material is conducted at a temperature of from about 270° C. toabout 330° C., and at a pressure of from about 4 (absolute) to about 7bar (absolute).

In an embodiment of the fourth aspect, the contacting with aheterogeneous hydrogenation catalyst occurs at a temperature of about150° C. to about 400° C., and the pressure of about 0.5 to about 10 bar(absolute).

In an embodiment of the fourth aspect, the step of contacting the secondreacted material is conducted at a temperature of from about 250° C. toabout 350° C., and at a pressure of from about 4 bar (absolute) to about7 bar (absolute).

In an embodiment of the fourth aspect, an alcohol-rich material and analcohol-depleted material are separated from the hydrogenated material,and the alcohol-depleted material comprises predominantly carbon dioxideand hydrogen.

In an embodiment of the fourth aspect, an alcohol-rich material and analcohol-depleted material are separated from the hydrogenated material;the alcohol-depleted material comprises predominantly carbon dioxide andhydrogen, and the alcohol rich material comprises at least 70 wt. %1-propanol.

In an embodiment of the fourth aspect, an alcohol-rich material and analcohol-depleted material are separated from the hydrogenated material,and the alcohol-depleted material comprises predominantly carbon dioxideand hydrogen; the alcohol-depleted material is treated viapressure-swing absorption to remove at least a portion of the carbondioxide present, resulting in a carbon dioxide-rich material and ahydrogen-rich material; and the hydrogen-rich material is recycled tothe step of contacting a gaseous material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a process for converting glycerol tomonohydric alcohols.

FIG. 2 is a schematic diagram of a process for converting glycerol tomonohydric alcohols with a combined dehydration-hydrogenation reactionstep.

FIG. 2 a is a schematic diagram of a process of FIG. 2 showing someoptional heat exchangers and blower.

FIG. 3 is a schematic diagram of a process for converting glycerol tomonohydric alcohols which incorporates a water-gas shift reaction intothe process.

FIG. 4 is a block diagram of an embodiment of the second separation stepof FIG. 1 which depicts a three-step separation process.

FIG. 5 is a block diagram of a process for converting glycerol tomonohydric alcohols where the process includes recycling ofunreacted/partially reacted species.

FIG. 6 is a block diagram of the process for converting glycerol tomonohydric alcohols where the hydrogenation reaction step takes place intwo steps.

FIG. 7 is a block diagram of a process for converting glycerol tomonohydric alcohols which utilizes steam reforming of at least a portionof an intermediate process stream to generate at least a portion of thehydrogen used in the process.

FIG. 8 is a graph showing the azeotropic composition ofwater-propionaldehyde at different pressures.

FIG. 9 is a block diagram of a process for converting glycerol tomonohydric alcohols utilizing an oxidative cleavage step followed byhydrogenation and dehydration reactions.

FIG. 10 is a block diagram of a process for converting glycerol tomethanol utilizing oxidative cleavage followed by a hydrogenationreaction without a dehydration reaction.

FIG. 11 is a chromatogram of the condensed product stream afterperforming sequential dehydration and hydrogenation on glycerol inseparate reactor beds with intermediate addition of hydrogen. Thisfigure shows the predominance of 1-propanol for reaction at 5 bar.

FIG. 12 is a graph of the relative concentrations of 1-propanol andpropionaldehyde in the condensed product stream for conversion ofglycerol to monohydric alcohols by sequential dehydration andhydrogenation with intermediate addition of hydrogen at differentpressures in the reactor set-up of FIG. 1. The concentration of1-propanol peaks, under the conditions tested, at about 4 bar (gauge).

FIG. 13 is a graph of the relative concentrations for acetaldehyde,acetone, methanol and ethanol in the condensed product stream forreaction at different pressures in the conversion of glycerol tomonohydric alcohols by sequential dehydration and hydrogenation withintermediate addition of hydrogen at different pressures in the reactorset-up of FIG. 1.

FIG. 14 is a graph of the relative concentrations of acetic acid andpropanoic acid for reaction at different pressures in the condensedproduct stream for the conversion of glycerol to monohydric alcohols bysequential dehydration and hydrogenation with intermediate addition ofhydrogen at different pressures in the reactor set-up of FIG. 1.

FIG. 15 is a graph of the equilibrium between propionaldehyde,1-propanol and acrolein at 1 bar for the sequentialdehydration-hydrogenation reaction system at different temperatures.This figure shows the condensed phase concentrations for the reactedproducts at 1 bar.

FIG. 16 is a graph of the equilibrium between propionaldehyde,1-propanol and acrolein at 4 bar for the sequentialdehydration-hydrogenation reaction system at different temperatures.This figure shows higher 1-propanol concentration at a given temperaturethan at 1 bar, in FIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description and examples illustrate a preferred embodimentof the present invention in detail. Those of skill in the art willrecognize that there are numerous variations and modifications of thisinvention that are encompassed by its scope. Accordingly, thedescription of a preferred embodiment should not be deemed to limit thescope of the present invention.

Conversion of Glycerol to Monohydric Alcohols

A process for converting glycerol as a byproduct of biodiesel productioninto more useful monohydric alcohols is provided. The process involvestwo reaction steps. In the first step, glycerol or other polyhydricalcohol(s) present in a biodiesel byproduct stream are dehydrated over asolid catalyst to yield acrolein and other dehydrated products.

In a second step, the dehydrated products are hydrogenated to yield,e.g., high value products including monohydric alcohols.

Under some reaction conditions, other intermediates can be produced,including glycols. The 3-carbon chain of the glycerol can also becleaved under certain reaction conditions, as discussed in detail below.Such intermediate cleavage products can include lower aldehydes. Theseintermediates can be further reacted to corresponding monohydricalcohols.

A process for producing monohydric alcohols from glycerol according to apreferred embodiment, which can be integrated into a biodieselproduction process, is depicted schematically in FIG. 1. A polyhydricalcohol feed 10 is subjected to dehydration conditions 1. The productstream 12, including acrolein and other dehydrated products, is thensubject to a separation step 2, whereby acrolein and aldehydes ingaseous form 14 are separated from less volatile components such aswater. The gaseous stream 14 is then subjected to hydrogenationconditions 3. Hydrogen 25 can be added to the gaseous products 14 priorto or at the separation step 2 and/or at the hydrogenation step 3 (ashydrogen 26). The resulting hydrogenated products 16 are subjected to afurther separation step 4, whereby a stream rich in monohydric alcohols20 is separated from another material that can contain unreactedglycerol and hydrogen and intermediates such as aldehydes, acrolein,hydroxy acetone, and the like. Although not depicted in FIG. 1, otherseparation and reaction steps can be employed in the process, as can therecycle of unreacted or only partially reacted species, and the use ofmultistage operations for one or more of these steps, as are appreciatedby one of skill in the art, and as is discussed in detail elsewhereherein.

Polyhydric Alcohol Feedstream

As discussed above, the methods and apparatus of preferred embodimentsare useful in converting glycerol as a byproduct in biodiesel productioninto higher value monohydric alcohols. Accordingly, a glycerol byproductstream from biodiesel production is a particularly preferred feedstream;however, any other suitable feedstream containing polyhydric alcoholscan be subjected to the process as described herein to yield highervalue monohydric alcohols. Examples of other such feedstreams include,but are not limited to, feedstreams from fat-splitting andtransesterification processes as well as streams that include glycerolfrom some other source, or glycols such as propylene glycol, ethyleneglycol.

The glycerol byproduct stream generated in biodiesel productionfrequently includes glycerol, methanol, catalyst(s), and othercompounds. If a different alcohol is used in the biodiesel productioninstead of or in addition to methanol, this alcohol could be present inthe byproduct stream instead of or in addition to the methanol. Theglycerol byproduct stream can be refined and purified, resulting in aprimarily glycerol/water mixture containing from about 20 to about 40wt. % glycerol. However, the particular methods and operating conditionsemployed can affect concentrations and compositions such that therelative amounts may vary. While a feedstream containing essentiallyglycerol (about 100 wt. %) is particularly preferred, polyhydricalcohols, more generally (for example, propylene glycol, ethyleneglycol, glycerol, etc.) and combinations of polyhydric alcohols are alsoacceptable. Feedstreams containing water and other impurities incombination with polyhydric alcohols can be processed, although forproduct purification purposes, it is generally preferred that thefeedstream be anhydrous or contain only a minimal amount of water.Typical polyhydric alcohol contents of feedstreams amenable to theprocesses of preferred embodiments are preferably at least about 5% orhigher, more preferably 10% or higher, and more preferably 20% orhigher, 30% or higher, 40% or higher, 50% or higher, 60% or higher, 70%or higher, 80% or higher, or most preferably 90 wt. % or higher.

While complicating purification, the presence of water can provide somebenefits. For example, it can act as a heat sink during processing whichcan moderate the reaction rates, it can facilitate reaction control, andit can facilitate broader reaction temperatures. Accordingly, in certainembodiments it can be desirable to have a water concentration in thefeedstream of preferably 95% or lower, more preferably 90% or lower, 80%or lower, 70% or lower, 60% or lower, 50% or lower, 40% or lower, 30% orlower, 20% or lower, or about 10% or lower by weight.

Other impurities that can be present in typical glycerol and polyhydricalcohol feedstreams include triacyl glycerides, partial glycerides,phospholipids, lysophospholipids, free fatty acids, soaps, sterols,salts, and the like. While it is generally preferred to minimize theamount of such impurities in the feedstream, the presence of a smallamount of these impurities is generally tolerable and will notsignificantly impact the production of monohydric alcohols.

It is generally preferred to minimize the salt content of thefeedstream. Preferred feeds have an ash value of approximately 2% orless, based on AOCS Test Method Ea 2-38 (American Oil Chemists'Society). Other feed materials acceptable for use can have approximately4-5% ash and others may have as much as 8% or 10% ash content or higher.The ash content can be due to residual catalyst from the production ofbiodiesel, to minerals present in the water used for processingbiodiesel, or to some other source such as carryover with the feed oil,or the like.

Phosphorus contaminants may also be present, such as from phospholipidsor lysophospholipids present in the feed oil or residualphosphate/phosphoric acid from processing. While it is desirable tominimize phosphate content, phosphate concentrations in the feed of lessthan about 5 ppm can be acceptable, and concentrations of about 5-100ppm or even higher can be tolerable.

Generally, contaminants such as phospholipids and salts, or volatilecontaminants with vapor pressures lower than glycerol do not presentissues for the processes of preferred embodiments, as they can besubstantially removed by vaporizing the feedstream. In some instances,careful selection of the vaporization conditions, such as temperature,pressure, water content, gas flow, and the like can enable theconcentration of contaminants in the gas phase to be minimized. Suchselections can be readily made by one of skill in the art afterexamination of the vapor pressure characteristics of the feed materialcomponents.

In certain embodiments, it can be desirable to further refine the feedmaterial, such as when the contaminants have an adverse effect oncatalyst life, activity or selectivity. Suitable refining methodsinclude, but are not limited to distillation, filtration, absorption,and adsorption methods.

Other contaminants include monohydric alcohols, such as are leftoverfrom transesterification operations, and hexane, heptane, and othersolvent remaining after oil crushing operations. These contaminants canbe removed, if desired, by e.g. volatilizing prior to vaporization ofthe glycerol in a flash tank, evaporator, still, or the like. However,in certain embodiments it can be acceptable for the contaminants toremain in the feed material and be removed in a downstream operation.Alcohol may also be present due to recycling/utilization of downstreammaterials.

The feedstream can be in any suitable state, such as gaseous, liquid,and/or vapor; however, it is generally preferred to use a gaseousfeedstream (or to convert a liquid or vapor feedstream to a gaseousfeedstream via heating or reduction of pressure) as a feed to the gasphase dehydration step.

Dehydration of Polyhydric Alcohols

The first step in the glycerol or polyhydric alcohol conversion processis typically a gas phase dehydration step over a suitable heterogeneouscatalyst. The dehydration reaction converts the glycerol, glycols, andother (poly)ols present in the feedstream primarily to acrolein, hydroxyacetone, aldehydes and alcohols. Suitable catalysts include those knownin the art for gas phase dehydration processes, including acids (e.g.,supported phosphoric or sulfuric acid), H-mordenite, Ce-mordenite,zeolite 13X, NH₄+ exchanged zeolite 13X, oxides of titanium, zirconium,hafnium, silicon, germanium, tin, cerium, thorium, aluminum, chromium,zinc, and tungsten as well as such oxides modified with an alkali metalor alkaline earth metal and/or an acidic material. Suitable catalystscan also include combinations of these individual catalysts, forexample, tungsten and cerium oxides (WO₃/CeO₂), tungsten and zirconiumoxides (WO₃/ZrO₂), tungsten and titanium oxides (WO₃/TiO₂), and tungstenoxides with mordenite (WO₃/mordenite). The catalyst can be supported ona suitable support such as a zeolite, alumina, kiselgur and/or silica;however, unsupported catalysts can also be desirable in certainapplications. The active part of the catalyst is typically only aportion of the catalytic particle, such as with 10% WO₃/TiO₂, 10%WO₃/CeO₂, 10% WO₃/ZrO₂, 25% (wt.) H₃PO₄/spinel, and 25% (wt.)H₃PO₄/alumina

A particularly preferred reactor for use in the dehydration step is aplug flow reactor (PFR) or tubular reactor with a fixed catalyst bed;however, any suitable reactor for use in dehydration can be employed.While continuous flow reactors are particularly preferred due to ease ofprocess integration, batch reactor configurations can also be employed.

The feedstream is preferably introduced into the dehydration reactor asa gas. If a liquid feedstream is employed, then it can be converted to agas by conventional methods, such as by heating or a reduction inpressure. The extent of reaction typically depends upon the specifictype and amount of catalyst, the feedstream composition, thetemperature, the pressure, the gas velocity, the degree of mixing, andthe reactor space time; however, it is generally preferred to operatethe reactor at a temperature of from about 220° C. to about 340° C.,more preferably from about 250° C. to about 310° C., a total pressure offrom about 0.1 bar to about 10 bar (absolute), more preferably fromabout 1 to about 7 bar (absolute), and most preferably from about 1 toabout 5 bar (absolute), and with a feed composition of from about 5 toabout 50 wt. % glycerol and from about 95% to about 50 wt. % water. Incertain embodiments, the reaction can be operated under differentconditions, such as at a temperature as low as about 200° C. or lower oras high as about 400° C. or higher. Under very low pressures (0.1 bar orlower), the reduced boiling points of glycerol and water can allowoperation of the reactor at lower temperatures (about 200° C. or lower).Similarly, low or reduced concentrations of glycerol can allow operationof the reactor at lower temperatures (about 200° C. or lower), as thepartial pressure of glycerol can still be kept below the saturationpressure of glycerol at the operating temperature. Higher temperatureand/or lower pressure can allow operation of the reaction at higherglycerol concentrations. Other conditions may be acceptable in certainembodiments, such as when a particular final alcohol composition isdesired. For example, higher pressures favor propanol and lowerpressures favor a mixture of C₁-C₃ monohydric alcohols (such aspropanol, ethanol, and methanol). The reaction mixture can be heated orcooled to control the reaction as it progresses through the catalyst,such as by using heating or cooling jackets or coils, electricalheaters, or by introduction of one or more other gases of the same or adifferent temperature.

Separation of Dehydrated Intermediates

The product stream 12 from the dehydration reactor is preferablysubjected to a separation step to remove components such as water andvarious side reaction products from the desired intermediates to yield aproduct stream rich in aldehydes, acrolein, and monohydric alcohols. Theseparator is preferably a condenser that condenses the water and otherhigh boiling components, thereby removing them from the gaseous productstream. While use of a condenser in the separation step is particularlypreferred, other processes as known in the art for removing undesiredcomponents of the product stream can also be employed, such asdistillation, solvent separation, adsorbents, reactive chemicals, andthe like.

When a condensation process is employed, the separation can be performedin a single condenser, or in multiple condensers optionally operating atdifferent temperatures and/or pressures. In a preferred embodiment, theinlet stream is cooled when it enters the separating chamber, resultingin partial condensation of the inlet stream. The condensed material isthen directed from the chamber as a separate stream from the remaininggaseous material. In other embodiments, the inlet stream is cooled priorto entering the separation chamber, or the inlet stream is compressed toa higher pressure prior to entering the separation chamber, the higherpressure resulting in partial condensation of the inlet stream.Alternatively, the inlet stream can be heated prior to compression toreduce condensation of the compressed stream, either in the vicinity ofthe compressor or prior to cooling to control the location at whichcondensation occurs.

In certain embodiments, a distillation apparatus separates the desireddehydrated intermediates from water and other impurities. Any suitabledistillation apparatus can be employed, for example, a packed column ora tray column. The inlet stream can be a gas stream or a fully condensedstream, or a partially condensed stream, and interchange of chemicalspecies occurs between the rising gas phase and a falling liquid streamof condensed material.

In other embodiments, while it is generally desirable to minimize thesecomponents, however, in certain embodiments it may be desirable tointroduce a noncondensable gas into the feed to the separation device orinto the separation device itself to assist in the separation of thedesirable intermediates and final products. Suitable gases include inertgases such as helium, argon, nitrogen, air, other gases includingreactive gases such as hydrogen, carbon monoxide, carbon dioxide, andhydrocarbons and mixtures thereof.

The temperature and pressure at which the separator is operated, as wellas the type of separator employed, impact the efficiency and productdistribution characteristic of the separation that occurs. Preferredtemperatures and pressures can be selected based on the composition ofthe inlet stream. The operating conditions are typically selected so asto provide a low level of losses of desirable intermediates and finalproducts to the waste stream and a low level of water and side productsin the gas stream subjected to further processing in, for example, thehydrogenation step. Although the presence of water in the hydrogenationstep usually does not present issues, it may be more difficult toseparate the water at a later process step; accordingly, it is generallypreferred to minimize the amount of water present in the hydrogenationstep. Separation conditions can generally be selected based on thecomposition of the feed and the vapor pressure characteristics of thefeed components and mixtures thereof. Water separation techniques ordevices can optionally be used as a part of the separation step. Suchwater separation methods include membrane techniques, adsorptiontechniques, desiccants, etc.

Hydrogenation of Intermediates to Yield Monohydric Alcohols

The second reaction step in the process of the preferred embodiments isa hydrogenation step. The intermediates product stream 14 fromseparation step 2 is mixed with hydrogen gas in a second reactor undersuitable process conditions, resulting in hydrogenation of unsaturatedcomponents in the intermediates product stream. Preferred hydrogenationcatalysts include those based on the platinum group metals (platinum,palladium, rhodium, ruthenium, osmium, iridium), nickel, and copper. Thecatalyst may be supported or unsupported. Suitable supports includealumina, silica, carbon, spinel, and other such materials. Suitablehydrogenation catalysts are manufactured by BASF Catalysts (Iselin,N.J.), Johnson Matthey (London, England), Sud-Chemie (Munich, Germany),Topsoe (Lyngby, Denmark) and others. The primary hydrogenation reactionsresult in the saturation of the carbon-carbon double bond of acroleinand reduce carbonyl groups present in aldehydes and acrolein to hydroxylgroups, yielding monohydric alcohols.

The hydrogen employed in the hydrogenation step can be added directly tothe hydrogenation reactor with the intermediates process stream, or atleast a portion of the hydrogen can be added to the intermediatesprocess stream at any other suitable point upstream, such as before,during, or after the first separation step. Hydrogen in limitedquantities can also be added with the initial feed. Alternatively, thehydrogen can be added in portions to a hydrogenation reactor withreaction taking place between hydrogen additions. Batch reactors can beadvantageously employed; however, continuous flow reactors such astubular or plug flow reactors are typically preferred. The hydrogenationreactor can optionally include one or more intermediate heaters,coolers, compressors, and combinations thereof. The reactor temperatureis typically from about 200° C. to about 290° C., but temperatures aslow as about 150° C. or less, or as high as about 400° C. or more may beused. The reactor pressure can be from about 0.1 bar (absolute) to about10 bar (absolute), more preferably from about 0.5 bar (absolute) toabout 7 bar (absolute), and most preferably from about 1 bar to about 5bar (absolute). The amount of hydrogen can be up to about two timesstoichiometric. However, higher levels such as up to about 10 timesstoichiometric can be advantageously employed, especially when provisionis made to recycle or recover the excess hydrogen.

In preferred embodiments, at least a portion of the heat generated inthe hydrogenation reaction is removed by heat transfer to coolingjackets or cooling coils. Alternatively, at least a portion of the heatof reaction can be removed by heat transfer to the surroundingenvironment. In other embodiments, the reaction proceeds in a sequenceof stages with cooling devices or heat exchangers between at least twoof the stages. Alternatively, the reaction rate can be controlled byaddition of hydrogen in stages, or by selecting an amount of coolingarea associated with a reactor.

Purification of Monohydric Alcohols

The second separation step 4 in the process shown in FIG. 1 is a partialcondensation or a step-wise condensation of the components of the outletstream from the hydrogenation reaction. For example, the stream can becooled to a temperature below the boiling point of the monohydricalcohols present. For methanol (boiling point 64.7° C. at 1 atmosphere),a temperature of about 60° C. at a pressure of about 1 atmosphere can bedesirably employed, with the resulting condensate removed.Alternatively, the stream can be cooled step-wise, first to about 140°C. at about 1 atmosphere (below the boiling point of hydroxyacetone) tocondense glycerol, glycols and hydroxyacetone that may be present, andthen to about 60° C. at about 1 atmosphere to condense monohydricalcohols that may be present, with removal of the resulting condensateat each step. In another embodiment, the first condensation step occursat a temperature sufficiently high to remain above the boiling point ofhydroxyacetone, such as from about 150° C. to about 185° C. at about 1atmosphere and the second condensation step occurs at a temperaturebelow the boiling point of any monohydric alcohols that are present.

In another embodiment, the outlet stream from the hydrogenation reactioncan be cooled first to condense the polyhydric alcohols at a temperatureof from about 150° C. to about 185° C. at about 1 atmosphere, thencooled to condense hydroxyacetone at a temperature of from about 100° C.to about 143° C. at about 1 atmosphere, then further cooled to atemperature of from about 58° C. to about 63° C. to condense monohydricalcohols with the resulting condensate removed at each stage. In certainembodiments, a fourth cooling step to condense and removecarbonyl-containing compounds by cooling to below the boiling point ofthe specific compound (for example, acetone at 56.5° C., acrolein at 53°C., propionaldehyde at 46-50° C.; acetaldehyde at 20.2° C., andformaldehyde at −19.3° C.).

The temperatures described above for the condensation stages are foroperation at about 1 atmosphere. The specific temperatures selected canreadily be adjusted for different operating pressures based on thechanges in the boiling points of the specific compounds present, withhigher temperatures generally used at higher pressures and lowertemperatures at lower pressures.

In certain embodiments, distillation equipment can be used with or inplace of the condensation/separation steps. The operating conditions forsuch distillation equipment are selected based on the boiling points ofthe various compounds present at the operating pressures.

Preferably, at least two condensation stages are employed with theoutlet stream from the hydrogenation step. The stream is first cooled tocondense glycols that are present, such that they are separated from gasphase monohydric alcohols. Preferably, at least about 50 wt. % of theglycols are condensed in the first condensation step, and this streammay contain hydroxyacetone. This step can be followed by condensation ofthe monohydric alcohols present. Preferably, at least about 50 wt. % ofthe monohydric alcohols are condensed in the second condensation step. Asubsequent condensation step can be employed to separate aldehydes andketones present. However, in certain embodiments, these aldehydes andketones can be condensed with the monohydric alcohols or they can remainwith the noncondensed stream or they can be divided with a portionremaining with the noncondensed stream and a portion condensing with themonohydric alcohols. When the aldehydes and ketones are condensed in aseparate stage, preferably at least about 50 wt. % of the aldehydes andketones present are condensed in the subsequent condensation step. Thespecific temperature of each step can be selected based on the operatingpressure and the boiling point of the compounds present. The glycerolcontaining stream is preferably recycled to the dehydration reactor, andthe aldehydes and ketones are preferably recycled to the hydrogenationreactor. When condensed in a separate stage, hydroxyacetone ispreferably recycled to the hydrogenation stage.

Cooling for the condensation steps can be achieved by any suitablemethod, such as the use of at least one heat exchanger, or through atleast one wall of the separator vessel. Alternatively, at least onedistillation column can be used to perform at least one separation ofthe product stream (or a fraction thereof) of the hydrogenationreaction. In other embodiments, at least one compressor is used in placeof or in addition to at least one cooler (for example, a heatexchanger). While condensers and distillation columns are particularlypreferred separators, other separation devices can also be employed, asare known in the art (for example, stills, cyclones, membranes, and thelike, and those based on absorption and adsorption principles).

Recycle Streams

The process can be operated in a “once-through” fashion, with no recycleof separated materials. However, in certain embodiments it can bedesirable to collect streams of separated materials or other materialsfrom different points in the process, either for recycle to differentpoints in the process of the preferred embodiments, as feedstock inother processes, for further separation or fractionation on otherequipment, for storage, and/or for use as a final product. For example,an effluent stream from the second separation step 4 can be recycled tothe first separator 2. The recycled stream can be a gas stream, and canoptionally contain (or consist only of) hydrogen gas. In anotherembodiment, an effluent stream from the second separation step 4 isrecycled to the first reaction step 1; for example, a recycle streamincluding one or more glycols is recycled to the first reaction step 1.In yet another embodiment, an effluent stream from the second separationstep is recycled to the second reaction step 3, for example, a recyclestream including hydroxyacetone.

Monohydric Alcohol Product Stream

The product stream composition can vary depending on a variety offactors, including how the second separation step is operated. Forexample, in one embodiment, only the residual gases noncondensible atatmospheric pressure and normal room temperature are removed. In thisparticular embodiment, the composition of the product stream can includemonohydric alcohols and incompletely reacted feed and intermediates. Theincompletely reacted materials can include, depending on the extent ofthe reactions, at least one of glycerol, glycols, aldehydes, andhydroxyacetone. Such mixed product streams can be useful in certainapplications, or can be useful for further processing at a differenttime or location to yield valuable products or intermediates.

Alternatively, the second separation step can separate thenoncondensible gases and one or more condensed liquid streams from theproduct stream. The composition of the streams can depend on theoperation of the second separation step, but generally, for thenoncondensible gas stream as described above, the condensed liquidstream composition typically contains at least one of glycols andglycerols. The product stream can also include monohydric alcohols,which are generally the most desirable products of the process. Otherintermediate products, such as aldehydes and hydroxyacetone can bepresent in the product stream, the condensed liquid stream, or bothstreams. Further, the aldehydes and hydroxyacetone can be presenttogether in one stream or separated between the streams, depending onthe operation of the second separation step. The condensed liquid streamcan be stored, used in certain applications, re-introduced into theprocess at a different times and/or locations, or recycled. In certainembodiments, the condensed liquid stream is recycled to the firstreaction step. The product stream can be used for a desired purpose, orstored.

In certain embodiments, the second separation step separates thenoncondensible gases and two condensable liquid streams from the productstream. The noncondensible gas stream is typically as described above.The two condensed liquid streams can be characterized as one rich inglycols and possibly glycerol with the other rich in hydroxyacetone. Theproduct streams are rich in monohydric alcohols. The condensed liquidstreams can be recycled to the process at, for example, the firstreaction step and/or the second reaction step, or they can be collectedfor other uses or processed at a later time or place.

The actual composition of the product stream when two other condensedliquid streams are to be produced therefrom preferably has a compositionthat depends upon the operation of the overall system. For example, atypical composition is desirably about 90% or more by weight monohydricalcohol with hydroxyacetone, propionaldehyde and othercarbonyl-compounds as possible contaminants. If the operation of thesecond separation step is changed such that a lower temperature isemployed for the hydroxyacetone separation, less hydroxyacetone islikely to be in the product stream, but additional losses of alcohol arepossible. If the temperature is increased, however, the amount ofhydroxyacetone in the product stream may increase. Alternatively,changes to the hydrogenation conditions can result in morealdehydes/ketones present in the product stream.

Process Modifications—Combined Dehydration and Hydrogenation

In another embodiment, the first reaction step can optionally involve acombination of dehydration and hydrogenation reactions. An additionalhydrogenation step can be performed downstream of this reaction step. Atleast a portion of the hydrogen used in the process can be added at thefirst reaction step, as illustrated in FIG. 1 with hydrogen stream 28,to, for example, improve the conversion of at least a portion of thepolyhydric alcohol to monohydric alcohol. For conversion of glycerol to1-propanol, the reaction equations are:

The propionaldehyde can then be converted to propanol in this reactionstep or in another.

Other alcohols or alcohol mixtures can be produced by varying thematerial fed to the reactor and/or changing the reaction conditions. Forexample, propylene glycol or ethylene glycol may be fed. Also, thereaction pressure can be varied, with higher pressures, for example,favoring conversions of glycerol to 1-propanol and lower pressuresfavoring conversion of glycerol to a mixture of ethanol, methanol, andpropanol with the first reaction step converting the glycerol to thecorresponding aldehyde or mixture of aldehydes.

Reactor 1 can include a mixed bed of hydrogenation and dehydrationcatalysts. Reactor 1 can also include a bed of dehydration catalyst(s)in series with a mixed bed of hydrogenation catalyst(s). Preferredhydrogenation and dehydration catalysts include those described above.In one embodiment, a mixed bed of approximately 90 wt. % dehydrationcatalyst and 10 wt. % hydrogenation catalyst is employed. In anotherembodiment, from about 10% to about 35 wt. %, or from about 35 wt. % toabout 55 wt. % of the mixed bed is hydrogenation catalyst. In yet otherembodiments, up to about 90 wt. % of the mixed bed is hydrogenationcatalyst. In embodiments wherein there is both a dehydration bed and amixed bed, these beds can be enclosed in separate reactor housings, orthey can be in a common housing. In further embodiments, there can bemore than one bed of a given type or there can be more than one bed ofeach.

When a mixed catalyst bed is employed, with or without a dehydrationcatalyst bed, it is typically preferred to feed at least a portion ofthe hydrogen gas to reactor 1, typically a sub-stoichiometric quantityof hydrogen based on complete conversion of glycerol to 1-propanol. Theamount of hydrogen fed is typically from about 40% to about 500% of thestoichiometric amount, but in some instances it can advantageously befrom as low as 10% or less to about 10,000% or more of stoichiometric.

In a preferred embodiment, an amount of hydrogen is employed in thefirst reaction step to achieve a high degree of conversion topropionaldehyde with a low degree of conversion to alcohol. For example,acrolein and propionaldehyde can be present in a weight ratio of fromabout 6:1 to about 0:10, or from about 1:1 to about 0:10, or even fromabout 3:7 to about 0:10, or from about 1.5:8.5 to about 0:10, or fromabout 0.1:10 to about 1:9. The amount of hydrogen that reacts in thisembodiment is typically about 1 mole per mole of glycerol; however, dueto the reversible nature of the reaction and the possibility of furtherreaction to alcohol, an amount somewhat in excess of about a 1:1 molarratio and below about a 1:2 molar ratio is generally be preferred.

Reducing the amount of acrolein in the product stream offers benefitsrelated to safety and ease of separation of water from the reactionmixture. When no hydrogenation takes place due to no hydrogenationcatalyst or no hydrogen, one of the primary reaction products isacrolein. Acrolein is generally an undesirable intermediate due to itsinstability, toxicity, and carcinogenicity. For safety reasons, it isdesired to maintain a relatively low concentration of acrolein in thesystem, and not conduct steps that result in its concentration.

If the water is not removed after the first reaction step, it is insteadremoved later in the process, such as after the hydrogenation step hasconverted intermediates to alcohols. Removal of the water at this laterpoint in the process can be significantly more difficult due to thepresence of compounds such as 1-propanol and ethanol which can formazeotropes with water and/or have boiling points significantly closer tothat of water and the intermediate acrolein. For example, the boilingpoint (at 1 atmosphere) of acrolein is 52.5° C., the boiling point of1-propanol is 97.2° C., the boiling point of ethanol is 78.5° C., andthe boiling point of propionaldehyde is 48.8° C.

Conversion of at least a portion of the acrolein to propionaldehyde inthe first reaction step can desirably reduce the concentration ofacrolein within the system generally, and also can facilitate theseparation of water by allowing the water to be separated from a streamcomprising propionaldehyde, such as stream 12, which has a relativelylower boiling point, instead of 1-propanol, which has a relatively highboiling point, or acrolein. Separation of water from propionaldehyderather than from 1-propanol has the further advantage of thepropionaldehyde-water azeotrope having a water content of only about 2wt. % instead of about 28 wt. % for 1-propanol at 1 atmosphere. One ofthe myriad advantages of the combined reactor configuration is that itsupports the isolation and removal of water prior to conversion ofintermediates into monohydric alcohol, which in turn reduces thecomplexity of achieving a high quality monohydric alcohol product streamwith little water present.

In a preferred embodiment of the mixed bed of hydrogenation anddehydration catalysts, sufficient hydrogen is added to the firstreaction step to balance the heat requirements of the endothermicdehydration with the heat generation of the exothermic hydrogenation.The amount of hydrogen reacted to approximately balance the heatrequirements will depend on the degree of conversion of the glycerol tovarious compounds at this point in the process, such as acrolein,propionaldehyde, propanol, formaldehyde, acetone, propanol, methanol,ethanol, and hydroxy acetone. The amount of heat lost through thereactor walls as well as any desired temperature rise or fall across thereactor can also be considered in balancing the heat required forendothermic dehydration with the exothermic hydrogenation. In someembodiments, the amount of hydrogen reacted to approximately balance theheat requirements can be about two-thirds to about three-fourths of amole of hydrogen per mole of glycerol. In other embodiments, the amountof hydrogen reacted can be about 0.03 to about 0.7 mole of hydrogen permole of glycerol or about 0.06 to about 0.5 mole of hydrogen per mole ofglycerol, or even about 0.1 to about 0.3 mol of hydrogen per mole ofglycerol. As discussed above, the actual amount of hydrogen ispreferably slightly in excess of this amount. At least partial balancingof the heat requirements for these reactions can improve the energyefficiency through direct utilization of the heat generated duringhydrogenation. The heat from the exothermic hydrogenation can also becollected, such as with heat exchangers, and used at other points withinthe process or for other uses entirely such as a heat source for theproduction plant, or the nearby locale.

In certain embodiments, the amount of hydrogen added to the firstreaction step can be adjusted based on various measurements such as therelative flow rates of glycerol and hydrogen, the outlet temperature ofthe reactor bed, comparison of the inlet and outlet temperature of thereactor bed, analysis of the reactor bed outlet stream composition, etc.

Alternatively, similar results can be achieved by using more hydrogenbut limiting the amount of catalyst, thereby effectively limiting theextent of hydrogenation that occurs at the first reaction step.Similarly, the different catalysts present within the combined bed canbe distributed so as to support proper thermal energy transfer andmanagement of the reactions taking place.

Single Reaction Step

In another embodiment, as depicted in the scheme of FIG. 2, all of thedehydration and hydrogenation takes place in a single reaction step,followed by separation steps to remove excess hydrogen and water. Thereaction step in this embodiment includes one or more reactor beds withdehydration and hydrogenation catalysts for gas phase conversion ofpolyhydric alcohols to monohydric alcohols. The conversion of glycerolto 1-propanol is accomplished according to the following net reaction:

C₃H₅(OH)₃+2H₂→C₃H₇OH+2H₂O

Different reaction conditions can lead to different products. Forexample, lower reactor pressures favor a mixture of alcohols.

FIG. 2 schematically shows an embodiment of such a process wherein theglycerol conversion occurs in reactor 355. In this embodiment, thefeedstream comprising glycerol and water is fed to reactor 355. Hydrogengas 332 is mixed with the glycerol feedstream in reactor 355 or beforethe reactor. The gaseous feedstream with hydrogen contacts catalyst inreactor 355 at about 300° C. Suitable catalysts are those that cansupport a multistep reaction, such as a mixture of dehydration catalystand hydrogenation catalyst as previously described. The reaction cantake place in two steps where the first step involves dehydration(removal of water) of the glycerol. Suitable catalysts for dehydrationreactions include acidic materials such as mineral acids, and phosphoricacid on various solid supports such as alumina or silica. Other acidicmaterials include solid acids such as γ-alumina, aluminum silicates,zeolites, and the like. In the second step, the dehydrated product ishydrogenated (hydrogen addition). Suitable hydrogenation catalystsinclude nickel and precious metals such as nickel, copper, and platinumgroup metals (platinum, palladium, rhodium, ruthenium, osmium, iridium,and the like). These two reaction steps are preferably combined, as witha mixed catalyst bed, but in some instances separate reaction beds foreach catalyst or a mixed catalyst bed and a bed with a single catalystcan be used together in a single reactor. In some embodiments, a reactorbed can be a reactive distillation column in which intermediate productsare condensed and recycled back to the hot inlet stage where they arevaporized again and mixed with feedstream 311 or added directly toreactor 355 and flow in contact with the catalyst. The propanol, waterand hydrogen mixture 356 passes out of reactor 355 to a condensingseparator 307 in which unreacted hydrogen 333 is isolated, andoptionally returned to reactor 355. The liquid propanol and watermixture 318 passes to the water removal module 308 in which the propanolis dried into a usable alcohol stream 319 and byproduct water stream341.

In other embodiments, various heat exchangers, vaporizers, coolers,condensers, blowers, and pumps can be used in the process. FIG. 2 ashows schematically one such embodiment with recuperative heat exchanger351, heater 353, and blower 309. In different configurations, variationscan be used, such as where recuperative heat exchanger 351 and/or heater353 can be incorporated into reactor 355. Similarly, coolers and/orcondensers can be integrated into condensing separator 307, or be madeseparate.

Water Gas Shift Hydrogen Supplementation

The water-gas shift reaction represents an equilibrium between carbonmonoxide and water on one side of the equation, and carbon dioxidehydrogen on the other:

The catalyst is preferably selected so as to reduce the operatingtemperature for this reaction. The reaction itself is well known, havingbeen studied for many years. Suitable catalysts include those based onFe/Cr, Cu/ZnO, Pt/Ce, and sulfides of Co/Mo. Different catalysts resultin different temperature requirements for the reaction. For example,typical operating temperatures when Fe/Cr catalyst is employed are inexcess of about 350° C., while those for Cu/ZnO are typically from about200° C. to about 300° C., and those for Pt/Ce are typically from about200° C. to about 500° C. Some of the catalysts require the presence ofadditional chemicals or agents to maintain activity. For example,sulfides of Co/Mo require the presence of sulfur in the reaction streamto maintain activity. In certain embodiments, these agents can be addedto the reaction mixture, they can be carried over from an earlierprocessing step with one of the reagents, such as for example, sulfatesor sulfuric acid being present in a glycerol feedstream after acidcatalyzed transesterification with sulfuric acid, or the agent can beleft out, and provision made for periodic regeneration of the catalyst.The agent can be removed in a downstream process step, or left in theproduct stream. In some embodiments, the agent is preferably recycled.As the catalysts are identified, their temperature requirements can bereadily ascertained, and employed within the process for producingalcohol.

The water gas shift reaction can be operated over a broad range ofpressures. Typically, it is run at a pressure of from about 1 bar toabout 20 bar. While the equilibrium is not strongly affected by thepressure, the reaction rate increases as the pressure increases due toincreased collisions between molecules. Operation outside of this rangeis also possible, and the actual operating pressure can be selectedbased on other parameters such as, for example, the pressurerequirements for processing steps upstream or downstream of the shiftreactor.

As shown in FIG. 3, a water-gas shift reaction can be employed toprovide hydrogen for the process. In the dehydration and hydrogenationreactors, side reactions can occur under various conditions whichresulted in the formation of carbon monoxide which when present can berecovered and recycled with residual hydrogen. In one embodiment, theside product carbon monoxide with residual hydrogen 61 is recycled tothe process downstream of the first reaction step 51. While FIG. 3depicts a water-gas shift reactor 52 employed in a system with acombined bed reactor and a hydrogenation reactor, it can be employed inany of the processes disclosed herein which utilize hydrogenation andhave, or can be made to have, carbon monoxide (CO) present. As such, itcan optionally be employed to provide or supplement the hydrogen for theprocess downstream of a dehydration reaction step, or a combinedreaction step, or downstream of an oxidative cleavage step. If one ofthese reaction steps is present, the water-gas shift reaction system canbe fitted to a recycle stream where CO and water is present. In certainembodiments, the process conditions can be adjusted to ensure sufficientcarbon monoxide is present for the amount of hydrogen to be made withthe water-gas shift reaction. In various embodiments, the processconditions can be adjusted to ensure most of the carbon monoxide presentundergoes the water-gas shift reaction to produce hydrogen for theprocess.

In the water-gas shift reaction integrated into the process shown inFIG. 3, carbon monoxide combines with water in a reactor 52 over acatalyst to produce hydrogen gas, carbon dioxide and water 62. Thehydrogen rich stream 62 is then separated 53 to remove water 63. Thewater depleted stream 64 is fed to the second reactor 54 forhydrogenation, in some embodiments with additional hydrogen 26 from thewater-gas shift system or from elsewhere. The hydrogenated mixture 65 isseparated to remove the alcohols and the gas stream 67, primarilycomposed of hydrogen, carbon monoxide and carbon dioxide, is separated56 by pressure swing adsorption to remove carbon dioxide 68, with thehydrogen and carbon monoxide recycled as stream 61.

The pressure swing adsorption unit 56 includes a zeolite-based adsorbentmaterial which adsorbs CO₂ at high-pressure and desorbs it when thepressure is reduced. The CO₂ depleted stream can be recycled as a sourceof hydrogen and CO within the process. The purged CO₂ stream can bevented to the atmosphere, or collected if desired. The high-pressureconditions are preferably from about 3 bar (absolute) to about 11 bar(absolute). Preferably, the low-pressure condition is at or nearatmospheric pressure. However, pressures higher or lower can be employedas long as the pressure is less than the high-pressure condition. Ifsub-atmospheric pressure is employed, blowers and/or compressors may berequired to handle the low-pressure gas stream.

Other operating steps in this embodiment, such as for the first reactor51, the separation steps 53, 55 and the hydrogenation reactor 54 arelargely similar to that described in other embodiments. In somecircumstances, somewhat different stream compositions can be employed.For example, the recycle of carbon monoxide and subsequent conversion ofcarbon monoxide to carbon dioxide in the water-gas shift reaction canincrease the amount of these compounds in the system.

FIG. 1, as described above, also illustrates as a block diagram oneembodiment of a process for converting polyhydric alcohols includingglycerol and glycols to monohydric alcohols. A feed material 10 whichincludes glycerol and water is reacted in a first reaction step 1 to atleast partially dehydrate glycerol in the feedstream. The feed materialis either in gaseous form or it is vaporized inside the reactor or priorto entering the reactor. Vaporization can be accomplished by increasingthe temperature or reducing the pressure of the stream, or by acombination of raising the temperature and lowering the pressure.Suitable temperatures are from about 200° C. to about 400° C. andsuitable pressures are from about 1 bar to about 7 bar (absolute).Preferred conditions for production of a 1-propanol rich product includetemperatures of about 265° C. to about 305° C. and pressures of about 4to about 7 bar (absolute). Preferred conditions for production of amixed alcohol stream, such as one including methanol, ethanol and1-propanol include temperatures of from about 250° C. to about 305° C.and pressures of about 1 bar (absolute).

The dehydration product stream 12 exits the reaction step and enters afirst separation step 2. The dehydration product stream 12 is at leastpartially condensed to produce a liquid stream 13 which contains atleast a portion of the water present in the reacted stream 12. Liquidstream 13 can also contain at least some of the impurities present thatare present in the feedstream 10 or generated in the reaction step 1.Condensation in separation step 2 can be accomplished by reducing thetemperature or raising the pressure, such as by compressing the gas, orby a combination of cooling and increasing the pressure. Such coolingand/or pressure increase can be accomplished within the separation step2 or prior to the reacted stream 12 entering the separation step 2.Hydrogen 25 can also be added to the separation step. Hydrogen 25 addedat this point can participate in the separation that takes place, forexample, by sweeping gas headspace present in the separation device orby reducing the partial pressure of other components in the separationstep 2.

The gaseous stream 14 leaves the separation step 2 and enters the secondreaction step 3. In the second reaction step 3, the gaseous stream 14,which can include aldehydes and alcohols, acetones and acrolein, reactswith hydrogen over a hydrogenation catalyst as previously described inan exothermic reaction. The hydrogen can be introduced in the firstseparation step 2, or at the second reaction step 26, or at both. Thehydrogen can also be added in portions, as with a multistage reactionstep where a portion of the hydrogen is added and allowed to react, thenan additional portion of hydrogen is added and allowed to react. Thesequence of adding hydrogen and reacting can be repeated for additionalstages of reaction. Optionally, the temperature of the reaction mixturecan be limited, reduced, or controlled by any suitable method and/orapparatus, such as by cooling the gaseous feed 14, cooling the equipmentsuch as with cooling jackets or coils, or adding cooling equipmentbetween the stages of the reaction step.

The reacted material stream 16 exits the second reaction step 3 andenters the second separation step 4. The reacted material stream 16 isat least partially condensed to produce a product stream 20 whichcontains at least one monohydric alcohol. The noncondensed material 27can contain non-reacted glycerol, incompletely reacted intermediates,such as aldehydes, acrolein, hydroxy acetone, and other compounds.Condensation in the second separation step 4 can be accomplished byreducing the temperature or raising the pressure, such as by compressingthe gas, or by a combination of cooling and increasing the pressure.Such cooling and/or pressure increase can be accomplished within theseparation step 4 or prior to the reacted material stream entering thesecond separation step 4.

The nature of the separation that occurs in the second separation step 4can be adjusted depending upon the operating temperature and pressure.For example, as the temperature is decreased, the pressure increased, orboth, more materials are condensed and the composition of the productstream 20 and the noncondensed 27 stream change.

In certain embodiments, the second separation step 4 can be operated asa multistage condensation with different liquid materials removed underdifferent condensation conditions to accommodate, for example, differentproducts, to provide better selectivity or better purity of a particularstream, or to better facilitate recycle of streams. Two, three, or morestages can be employed. In certain embodiments, more than one stage canuse the same conditions. FIG. 4 illustrates an embodiment of amultistage second separation step that includes three condensationsteps. The reacted material stream 16 is cooled with cooling step 131,and enters the first stage separation step 101. Liquid stream 21, whichincludes glycols, is removed from the gaseous stream 114. The operatingconditions of first stage separation step 101 are, for operation at 1atmosphere, a temperature of preferably from about 150° C. to about 185°C. based on the boiling points of glycerol, propylene glycol, ethyleneglycol and hydroxyacetone. For operation at other pressures, thetemperature can be adjusted based on the change in boiling point of thematerials being separated.

Gaseous stream 114 is further cooled in cooling step 132 and enters thesecond stage separation step 102. Liquid stream 24, which includeshydroxyacetone, is removed from the gaseous stream 117. The operatingconditions of second stage separation step 102 are, for operation at 1atmosphere, preferably about 100° C. to about 143° C. based on theboiling points of hydroxyacetone and the monohydric alcohols present. Iflittle or no 1-propanol is present, a temperature of from about 80° C.to about 143° C. is employed. For operation at other pressures, thesetemperatures can be adjusted based on the difference in boiling point ofthe materials being separated.

Gaseous stream 117 is further cooled in cooling step 133 and entersthird stage separation step 103. Liquid stream 20 which includes one ormore monohydric alcohols is removed from the gaseous stream 22 whichincludes hydrogen gas. The operating conditions of third stageseparation step 103 are, for operation at 1 atmosphere, a temperature ofpreferably from about 58° C. to about 62° C., depending upon the boilingpoints of the monohydric alcohols present and the aldehydes and ketonespresent. In certain embodiments, the presence or absence of particularcompounds enables operation at somewhat different temperatures. Forexample, if there is little or no acetone present, but acrolein ispresent, the low end of the temperature range can be as low as about 55°C. Similarly, if little or no acetone or acrolein is present, the lowend of the temperature range can be as low as about 52° C. For operationat other pressures, these temperatures can be adjusted based on thedifference in boiling point of the materials being separated.

In further embodiments, materials separated from the process can berecycled back into the process. FIG. 5 shows one embodiment wherein thestreams from a three stage second separation step 4, such as is shown inFIG. 3, are recycled into the process. Liquid stream 21 is recycled tothe first reaction step 1. Gaseous stream 22 is recycled to the firstseparation step 2. Liquid stream 24 is recycled to the second reactionstep 3. FIG. 6 shows another embodiment where the second reaction steptakes place in two-steps 3A and 3B. In addition, optional heat exchangedevices 41, 42, and 43 are used to adjust the temperature of the feed 15to the reactor 3A, and intermediate stream between reactor stages 17 andthe final reacted stream 16 from the second reaction step. Optional heatexchange devices 41, 42, and 43 can be used, for example, asinter-coolers between stages within reactor 3, or as heaters if desired.Such heat exchange devices, when used, can be present between somereactor stages and absent between others or they can be present betweenall reactor stages.

Alternative embodiments can optionally include steps such as routing thegaseous stream 22 to the first reaction step 1, and routing the gaseousstream 22 to the second reactor step 3. When gaseous stream 22 isrecycled within the process, it may permit a reduction in the amount ofhydrogen added at 25 or 26, in that the product is already at leastpartially hydrogenated. Other streams can be directed to other locationsas well. For example, liquid stream 24 can be recycled to the firstreaction step 1.

Recycle of process streams and fractions thereof can also be employedelsewhere in the process. For example, with a single stage secondseparation step, gaseous stream 22 can be recycled as described above.

Additional embodiments include storage of the liquid streams removedfrom the second separation step 4 and processing of the stream at adifferent time or location. The material separated can be recycled intothe process at a later time or run in the process separately from freshglycerol feed material.

In other embodiments, hydrogen can be generated on-site for use in theprocess. The hydrogen can be generated, for example, internally withinthe combined reactor bed 1 by integrating a small amount of reformingcatalyst, such as are known to those having skill in the art, into themixed catalyst bed, or at the start of the mixed catalyst bed. Thisapproach could provide a small amount of hydrogen, such as is needed toconvert the acrolein into propionaldehyde but insufficient amounts topromote the production of monohydric alcohols.

In other embodiments, larger amounts of hydrogen can be generatedon-site in other configurations as illustrated in FIG. 7. In FIG. 7hydrogen is formed by steam reforming a portion of the intermediatestream after the first reactor 51 to hydrogen and carbon monoxide butprior to the first separation step. This hydrogen is then available tohydrogenate other compounds within a later hydrogenation step. Thepresence of aldehydes and acroleins after the first reactor makes thisstream well-suited for steam reforming, especially when water vapor ispresent as well. To control the amount of hydrogen generated and theamount of intermediate products consumed, in one embodiment, a portionof the first reactor 51 outlet stream 12 is diverted as stream 71. Thisdiverted stream can be reintroduced prior to the water gas shift reactor52 as stream 72 or after the water gas shift reactor as stream 73,depending on the amount of carbon monoxide byproduct generated in thefirst reactor 51. Another advantage of this configuration is itsintegration with the gas phase separation 56 which can be, for example,a pressure swing adsorption unit. After the second separation step 55 inwhich the product liquids 20 are isolated from the gaseous compounds,the gaseous stream 56 is passed to a gas phase separation to removecarbon dioxide from hydrogen and carbon monoxide. To achieve removal ofthe majority of the carbon dioxide, some hydrogen and carbon monoxidecan exit with the exhaust stream 68. These gases can combusted inreactor 75 to generate heat which is needed for the endothermic steamreforming step in reactor 70. With this configuration, an overallincrease process efficiency can be achieved and hydrogen can beeliminated or reduced as a feedstock from the process.

In certain embodiments, the process is tailored to employ a diluteglycerol solution. For example, a 20 wt. % glycerol solution is fed to afirst combined dehydration and hydrogenation reactor, at a pressure offrom about 5 bar (absolute) to about 7 bar (absolute). The inlettemperature of the combined reactor is from about 280° C. to about 300°C. and the glycerol/water mixture is co-fed with hydrogen. Theintroduction of hydrogen into the reactor enables a lower inlettemperature to be employed than if acrolein was to be produced.Balancing the endothermic dehydration of glycerol to acrolein with thehydrogenation of acrolein to propionaldehyde yields a more eventemperature gradient over the dehydration section of the mixed bedreactor. The far end of the combined reactor can be configured for afinal hydrogenation wherein the temperature is increased to from about350° C. to about 400° C. This elevated temperature provides benefitssuch as better heat exchange of the outlet with the inlet streams, andsuppression of the formation of 1-propanol in the reactor due to theequilibrium that is maintained.

After leaving the combined reactor, the gaseous reaction mixtureconsisting of water, propionaldehyde, acrolein and traces of otherbyproducts such as propionic acid and hydroxyacetone is cooled. Aftercooling, the gas is mixed with a surplus of hydrogen and carbon monoxideand is passed through a water-gas shift reactor where the carbonmonoxide is reacted with water to form carbon dioxide and hydrogen.

The reaction mixture is then cooled further and introduced into adistillation column. The distillation of the mixture can be conducted ina regular distillation column, where it is distilled at about the systemoperating pressure. This yields a top volatile fraction rich inpropionaldehyde. Purity of the propionaldehyde (also known as propanal)stream may be limited by a propionaldehyde-water azeotrope, as shown inFIG. 8.

The separation can be further improved by the use of hydrogen as a sweepgas. Many high boiling compounds, such as propionic acid and the like,can be removed in the still bottoms along with water. Carry-over ofintermediate boiling components is more dependent upon the column designand operation.

The volatile stream from the distillation typically contains mainlypropionaldehyde and a small amount of water. This stream can be reheatedusing heat within the process or from an external source, and introducedinto a hydrogenation reactor. In the hydrogenation reactor,propionaldehyde and acrolein are reacted to form 1-propanol. Othershorter chain aldehydes are also reacted to form ethanol and methanol.The reaction is exothermic by nature and the reaction products arecooled, for example, in a constantly cooled tube reactor or severalreactors with inter-cooling, using the inlet glycerol/water mixture. Inthe hydrogenation reactor there is some formation of byproducts such aspropionic acid, dipropylether, and carbon monoxide. The residence time,catalyst and temperature in this reactor, as well as the chemicalspecies present, determines the amount of carbon monoxide and othercompounds formed. The resulting stream contains 1-propanol, ethanol,methanol, water, surplus hydrogen, carbon monoxide, carbon dioxide, andtraces of byproducts such as propionic acid. The resulting mixture ispassed through a condenser where 1-propanol, other short chain alcohols,water, and byproducts are separated out and the resulting solution has1-propanol content above 90% by weight.

The non-condensing gases are led to a pressure swing adsorber (PSA)where the carbon dioxide is separated together with a small part of thecarbon monoxide and hydrogen, while the rest of the hydrogen and carbonmonoxide is recirculated to the process.

Integration of the Water-Gas Shift Reaction into Production ofMonohydric Alcohol from Glycerol

The water-gas shift reaction enables hydrogen gas to be generated fromcarbon monoxide and water. Conversion of glycerol to monohydric alcoholsrequires hydrogen. FIGS. 3 and 7 illustrate a process for convertingglycerol to monohydric alcohol which utilizes the water-gas shiftreaction to supply at least a part of the necessary hydrogen. In certainembodiments, this conversion can take place by converting glycerol toacrolein, and then acrolein to propionaldehyde prior to the finalconversion to 1-propanol. These first two-steps are shown below:

C₃H₈O₃→C₃H₄O+2H₂O

(Dehydration of glycerol to acrolein—endothermic)

C₃H₄O+H₂→C₂H₆O

(Hydrogenation of acrolein to propionaldehyde—exothermic)

These two reactions can take place in the combined reactor with acombined dehydration and hydrogenation catalyst supplied with hydrogen.If about 60% to about 80% of the acrolein is converted topropionaldehyde, the reaction is auto-thermal (the endothermic reactionheat requirements are fulfilled by the exothermic reaction).

The efficiency of the conversion of glycerol to monohydric alcohols,such as 1-propanol, with the hydrogen provided by the water-gas shiftreaction can be evaluated as described below. Analysis of other speciesis analogous, with a similar overall efficiency.

In the first step, glycerol is converted to carbon monoxide andhydrogen:

C₃H₈O₃→3CO+4H₂

(Reforming of Glycerol)

This reaction is subsequently followed by the water-gas shift reaction:

3CO+3H₂O→3CO₂+3H₂

(Water-Gas Shift Reaction)

A total of 7H₂ molecules are formed for each glycerol moleculeconverted. This hydrogen is then available in the reaction of glycerolto propionaldehyde (equations shown above) and for the hydrogenation ofthe propionaldehyde to 1-propanol:

C₃H₆O+H₂→C₃H₇OH

(Formation of 1-Propanol)

The net equation for conversion of glycerol to 1-propanol withproduction of hydrogen by glycerol is:

9C₃H₈O₃→7C₃H₇OH+8H₂O+6CO₂

(glycerol to propanol with internal hydrogen generation)

The net equation shows the theoretical value for conversion efficiencyof glycerol to 1-propanol to be seven-ninths, or about 80%. Actualefficiency is likely lower (e.g., about 60% or less). Conversionefficiencies of glycerol to other monohydric alcohols can be determinedin a similar fashion, and similar efficiencies are expected.

Gas Phase Oxidative Production of Methanol and Ethanol

FIG. 9 schematically illustrates a gas phase glycerol conversion processof a preferred embodiment wherein glycerol is converted into amethanol-ethanol mixture of alcohols by a gas-liquid phase process 100employing intermediate aldehyde compounds and relatively lowtemperatures, e.g., under 400° C. In this embodiment, the glycerol 111is fed to an oxidative cleavage reactor 102 along with a source ofoxygen, such as air 121. Suitable catalysts (e.g., rhodium or chromium)support the oxidative cleavage of the carbon-carbon bond in vicinaldiols, producing smaller aldehydes:

R₁(CHOH)(CHOH)R₂+½O₂→R₁CHO+R₂CHO+H₂O

-   -   Wherein R₁ and R₂ are independently selected from the group        consisting of hydrogen, C₁₋₄ alkyl, C₁₋₄ alkene, C₁₋₄ alkyne,        C₁₋₄ hydroxyalkyl, C₁₋₄ hydroxyalkene, C₁₋₄ hydroxy-alkyne,        benzyl, phenyl, substituted benzyl, and substituted phenyl        groups.

To produce alcohols, the aldehydes can be reduced with hydrogen gas overa suitable catalyst. Catalysts for hydrogenation are the same asdiscussed previously. The hydrogenation reaction is represented by thefollowing reaction scheme.

R—CHO+H₂→R—CH₂OH

When the starting material is glycerol, the first reaction step involvesformation of formaldehyde (CH₂O) and glycolaldehyde (2-hydroxyethanal,CHOCH₂OH), such as through a partial oxidation reaction with oxygen in agas-liquid phase relatively low temperature, low pressure catalyticreactor. Typically the oxygen can be obtained from air, purified air,pure oxygen, or a combination thereof. If air or oxygen-depleted air isused, nitrogen will flow through the process as a dilution gas. If pureoxygen is desired the oxygen can be removed from air with a variety ofknown methods including pressure swing adsorption, membrane techniques,electrochemical techniques, and others. Electrochemical techniques canprovide an active catalyst surface with the ability to preciselyregulate the quantity of oxygen present at the catalyst surfaces. Theoxygen cleavage reaction is the following:

C₃H₅(OH)₃+½O₂→CH₂O+CHOCH₂OH+H₂O

As shown in FIG. 9, glycerol 111 and oxygen source (for example, air)121 are fed to the oxidative cleavage reactor 102 where the triol isconverted to formaldehyde and glycolaldehyde. The reaction is exothermicand the catalyst reactor is managed at temperatures of from about 100°C. to about 400° C. Suitable catalysts include various rhodium, chromiumor other salts in homogenous phase, in solid form, or supported on solidmaterial such as alumina, silica, carbon, and the like. Since theformaldehyde and water have low boiling points, the formaldehyde andwater are vaporized with heat from the reaction and purged from thereactor with depleted air to condenser-separator 103, in which thevaporized aldehyde and water are condensed and removed throughconnection 114 and the depleted air is passed out of the process instream 123. Alternatively, if all the oxygen is reacted, the nitrogenfrom the depleted air can also flow through stream 114 and function asdilution gas. Since the glycolaldehyde has a much higher boiling point,it remains in the liquid phase along with non-reacted glycerol. When theliquid phase has undergone sufficient conversion (sufficient residenttime in a tank or reaction time in a batch reactor) to convert most ifnot all of the glycerol, the glycolaldehyde remains as a liquid andexits the reactor 102 through connection 112, is mixed with thecondensed formaldehyde-water stream 114 and is fed to thereduction-hydrogenation reactor 104. In one embodiment, a reactivedistillation column can be used for the oxidative cleavage step 102.

The second step is a combined hydrogenation/dehydration step in thereactor 104, wherein the aldehydes are reduced to alcohols. Theformaldehyde reacts with hydrogen to form methanol according to thefollowing reaction.

CH₂O+H₂→CH₃OH

The glycolaldehyde also reacts with hydrogen to form the intermediateethanediol (ethylene glycol, HOCH₂—CH₂OH), which can be furtherdehydrated and hydrogenated to produce ethanol. The dehydration stepresults in the formation of vinyl alcohol (CH₂═CHOH) and water, whichfurther reacts with hydrogen to form ethanol. The resulting stream ofmethanol, ethanol, and water is removed from the process. The reactionsteps are as follows.

CHO—CH₂OH+H₂→HOCH₂—CH₂OH

HOCH₂—CH₂OH→CH₂═CHOH+H₂O

CH₂═CHOH+H₂→CH₃CH₂OH

As shown in FIG. 9, the mixed aldehyde solution enters thereduction-hydrogenation reactor 104 in which the formaldehyde reacts toform methanol and the glycolaldehyde reacts to form ethanediol. Thisgas-liquid stream is passed to the hydrogenation-dehydration reactor 106in which the water is chemically removed from the diol followed by thehydrogenation to form ethanol. The mixed stream 117 consisting ofmethanol, ethanol, water, trace non-reacted compounds, and hydrogen,flows to the condenser-separator 107. The hydrogen gas 133 is separatedfrom the liquids, mixed with feed hydrogen 131 and is passed to pump109, in which pressure is increased and the feed hydrogen is passed toreactor 104. The liquids are passed to water separator 108 in whichwater is isolated from the mixed alcohol stream and removed. The waterseparation can be a distillation and/or a desiccation process. Theproduct alcohol stream 119, which is primarily ethanol and methanol, canbe fed to a biodiesel reactor 2 to supplement or replace a fresh alcoholfeedstream.

Periodate Route for Production of Alcohols (Methanol)

A liquid phase oxidation scheme using periodate ion can also be used tooxidatively cleave the polyhydric alcohol to carbonyl-containingcompounds in a reaction analogous to the oxidation described above.

R₁—CHOH—CHOH—R₂+IO₄ ⁻→R₁—CHO+R₂—CHO+IO₃ ⁻+H₂O

However, regeneration of the periodate ion does not readily occur byoxidation with air or oxygen, but can be achieved through anelectrochemical mechanism.

It has now been found that a continuous process for oxidative cleavageof polyols using periodate ion can advantageously be employed when anexternal electric source for regeneration as an electrolytic cell isprovided. The half reactions are as shown below.

Anode: IO₃ ⁻+H₂O→IO₄ ⁻2H₂ ⁺2e ⁻

Cathode: 2H⁺2e ⁻→H₂(g)

Operation of the cleavage reaction in an electrolytic cell permitssimultaneous oxidative cleavage of a polyhydric alcohol, such asglycerol, and regeneration of the periodate ion. Subsequenthydrogenation of the carbonyl containing compounds, such asformaldehyde, can be carried out as described elsewhere to producemonohydric alcohols. The net reaction is:

R₁—CHOH—CHOH—R₂→R₁CHO+R₂—CHO+H₂

wherein R₁ and R₂ are as defined above. The hydrogen generated duringthe cleavage can be used to convert the carbonyls to alcohols, such asby methods described herein. Alternatively, the hydrogen can be used forother purposes including as a fuel and as a reagent in other reactions.

Gas Phase Production of Methanol by Oxidative Cleavage

If the second reaction step of the gas phase oxidative production ofmethanol and ethanol, described herein, is changed from ahydrogenation/dehydration step to a hydrogenation step solely, after onepass through the two reactors, glycerol is converted primarily toethanediol and methanol. These compounds are readily separated byvarious means including, for example, distillation due to the differencein their boiling points. The diol can then be returned to the oxidativecleavage step and split into formaldehyde.

HOCH₂—CH₂OH+½O₂→2CH₂O+H₂O

FIG. 10 is block diagram depicting such a process schematically.Glycerol 211 and air 221 are reacted in an oxidative reactor 202. Thedepleted air with some volatile species 213 is condensed 203 to recoverreacted intermediates 214. The depleted air 223 is removed or can passthrough the process as a dilution gas. The reaction mixture 212 from theoxidative reactor 202 is combined with stream 214 and fed tohydrogenation reactor 204 with hydrogen stream 232. The gaseous reactionproducts and unreacted hydrogen 215 are separated in condenser 205. Theliquid phase containing ethanediol is returned to the oxidative reactor202. The gas phase 216 containing methanol, hydrogen, and other gasesare separated in condenser 207. The hydrogen-rich gas phase 233 is mixedwith additional hydrogen 231 and compressed 209. The hydrogen feed 232is sent to the hydrogenation reactor 204. The liquid phase 218 fromcondenser 207 is separated 208 into an alcohol-rich stream 219 and aprimarily water stream 241.

Production of Hydrogen from Glycerol

Hydrogen can be generated on-site by the catalytic dehydrogenation ofhydrocarbons, yielding more unsaturated hydrocarbon chains:

C_(n)H_(m)→C_(n)H_(m-o)+½H₂  (7)

Analogous reactions can take place with other molecules, such asalcohols, fatty acid esters, aldehydes, and ketones.

This dehydrogenation can be carried out with a nickel catalyst at lowpressure and high temperature and is slightly endothermic (10 kJ/mol forC₁₂H₂₆ to C₁₂H₂₄). There are several alternative feedstocks for such aprocess, including glycerol and biodiesel.

In an embodiment utilizing biodiesel as the feed, a fraction of theproduct feed can be taken and the saturated diesel hydrocarbons can bestripped of some of their hydrogen. The size of this split-stream can beadjusted, for example, a small stream can be deeply dehydrogenated or alarger stream can be lightly dehydrogenated depending upon what productis desired. For example, if about 15% of the biodiesel product isdehydrogenated, a highly aromatic product results along with productionof sufficient hydrogen to convert the glycerol to methanol for thetransesterification reaction. In another embodiment, the side productsfrom conversion of glycerol to monohydric alcohol can be employed.

In certain embodiments, the dehydrogenated hydrocarbons can be burned tosupply heat for the process. Dehydrogenated compounds can also beblended into the biodiesel product, or used for other purposes asdetermined by their composition.

Example 1 Combined Reactor

A liquid feed of 20% technical grade glycerol in deionized (DI) waterwas fed at 18 g/hr through a flowmeter to a preheater where it wasvaporized and heated to approximately 290° C. The glycerol-water feedwas combined with 100 ml/min (25° C., 1 atmosphere) hydrogen and fed toa reactor bed. The reacted product stream from the reactor bed wascondensed and the liquid condensate analyzed. The flowrates of thecondensed liquid stream and the noncondensible gases were measured.Reactor pressure was held at approximately 6 bar (absolute). The reactorbed contained two zones of catalyst. The first zone (closest to the feedinlet) contained dehydration catalyst (WO₃/ZrO₂, 1 mm bead). The secondzone contained and equal amount of a mixture of 90% dehydration catalyst(WO₃/ZrO₂, 1 mm bead) and 10% hydrogenation catalyst (Topsoe, 1 mmgrain).

The condensed liquid stream was analyzed by gas chromatography with aCP-3800 gas chromatograph (Varian Inc., Palo Alto, Calif.) operatingwith a He mobile phase. Column temperature was ramped from 80° C. to250° C. Peaks were determined with a flame ionization detector.

The condensed liquid stream had the following composition.

Compound Retention time (Min.) Quantity (Area %) Acetic aldehyde 3.2411.66 Propionaldehyde 3.42 36.96 Acetone 3.50 4.96 Acrolein 3.60 5.08Methanol 3.74 4.89 Ethanol 3.90 2.18 Unknown 4.17 1.54 1-propanol 4.535.56 2-propanol 5.17 1.72 Unknown 6.94 1.92 Hydroxyacetone 7.12 5.99Unknown 8.13 1.20 Propionic acid 8.72 3.88 Valeric acid 9.96 8.57Unknown 11.57  3.89 Total — 100.00

Example 2 Dehydration Reactor

The experimental set-up and operation were as described in Example 1,except that no hydrogen was added. The condensed liquid stream had thefollowing composition and illustrates the higher production of acrolein.

Compound Retention time (Min.) Quantity (Area %) Acetic aldehyde 3.232.21 Propionaldehyde 3.41 7.61 Acrolein 3.58 50.42 Unknown 4.16 1.332-pentanol 5.16 4.24 Hydroxyacetone 7.11 23.16 Valerie acid 9.95 11.03Total 100.00

Example 3 Dehydration Reactor and Hydrogenation Reactor

A solution of 20% glycerol (technical grade) in DI water at 0.3mL/minute was heated and vaporized and fed to a first tubular reactor(25 mm diameter, 250 mm length) containing 39 mL (60 g) of 10% WO₃/ZrO₂dehydration catalyst (1 mm grains), then to a second tubular reactor (12mm diameter, 250 mm length) containing 12 mL (11 g) of Topsoehydrogenation catalyst (1 mm grains). Between the two reactors, 400mL/minute (1 atmosphere, 25° C.) of hydrogen was added. The firstreactor inlet temperature was 307° C. and the outlet temperature was260° C. The second reactor inlet temperature was 205° C. and the outlettemperature was 250° C. Both reactors were operated at 5 bar (absolute).After exiting the second reactor, the gas stream was condensed and thecondensate analyzed by gas chromatography as in Example 1. Thechromatogram is shown in FIG. 11, which indicates the high conversion topropanol.

Example 4 Effect of Pressure

The effect of different operating pressures on the product compositionwas evaluated with a reactor set up as described in Example 3. Reagentsand reagents flow rates were as in Example 3. The first reactorinlet/outlet temperatures were 290° C. and 285° C., respectively. Thesecond reactor inlet/outlet temperatures were 235° C. and 265° C.,respectively. The reactor operating pressure was varied from 0-6 bar(gauge). The analytical results for 1-propanol and propionaldehyde inthe product stream are shown in FIG. 12.

Analytical results for acetaldehyde, acetone, methanol, and ethanol areshown in FIG. 13. This graph shows that under these reaction conditions,alcohol selectivity for 1-propanol increases up to about 4 bar (gauge).Analytical results for acetic acid and propanoic acid in the productstream are shown in FIG. 14.

Example 5

The temperature and pressure dependence of thepropionaldehyde/1-propanol/acrolein equilibrium were determined using afree energy analysis for a reaction mixture of 1 mole acrolein, 25 moleswater, and 150 moles hydrogen at 1 bar (absolute) and 4 bar (absolute)and various temperatures are shown in FIGS. 15 and 16. These graphs showthat as the temperature increased, there is less 1-propanol and morepropionaldehyde present at equilibrium. In addition, as pressuresincreased the equilibrium shifted to the right, resulting in more1-propanol, and less propionaldehyde.

While it is generally preferred to operate the process according to thesequence of steps as depicted in the figures, in alternative embodimentsthe steps can be conducted in different order, or combined. For example,the two reaction steps can be done prior to any substantial separationstep, or the two separation steps may be combined into one overallseparation step. Additional processing can also be performed on themonohydric alcohol rich stream to purify it, to separate variousalcohols, to remove water, to react the alcohols, to combine it withother materials, or any combination of these additional processingsteps. For example, in one embodiment, the monohydric alcohol richstream can be treated to remove at least some of the residual water andthen combined with a diesel or biodiesel material. In anotherembodiment, the monohydric alcohol rich stream may be treated to removeat least some residual water and then esterified, or trans-esterified tofatty acids.

All references cited herein are incorporated herein by reference intheir entirety. To the extent publications and patents or patentapplications incorporated by reference contradict the disclosurecontained in the specification, the specification is intended tosupersede and/or take precedence over any such contradictory material.

The term “comprising” as used herein is synonymous with “including,”“containing,” or “characterized by,” and is inclusive or open-ended anddoes not exclude additional, unrecited elements or method steps.

All numbers expressing quantities of ingredients, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe specification and attached claims are approximations that may varydepending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should be construed in light of the number ofsignificant digits and ordinary rounding approaches.

The above description discloses several methods and materials of thepresent invention. This invention is susceptible to modifications in themethods and materials, as well as alterations in the fabrication methodsand equipment. Such modifications will be apparent to those skilled inthe art from a consideration of this disclosure or practice of theinvention disclosed herein. Consequently, it is not intended that thisinvention be limited to the specific embodiments disclosed herein, butthat it cover all modifications and alternatives coming within the truescope and spirit of the invention as embodied in the attached claims.

1. A method for converting glycerol to monohydric alcohol, the methodcomprising: contacting a gaseous material comprising glycerol with aheterogeneous dehydration catalyst at a temperature and a pressuresufficient to convert at least a portion of the glycerol to one or morecompounds having at least one of a carbon-carbon double bond and acarbon-oxygen double bond, whereby a dehydrated glycerol material isobtained; adding hydrogen gas to the dehydrated glycerol material;contacting the mixture of hydrogen gas and dehydrated glycerol materialwith a hydrogenation catalyst at a temperature and a pressure sufficientto convert at least a portion of the compounds having at least one of acarbon-carbon double bond and a carbon-oxygen double bond to one or moremonohydric alcohols, whereby a hydrogenated mixture is obtained; andseparating a monohydric alcohol-rich portion from the hydrogenatedmixture.
 2. The method of claim 1, wherein the monohydric alcohol-richportion comprises at least 75 wt. % monohydric alcohols
 3. The method ofclaim 1, wherein the monohydric alcohol-rich portion comprises at least70 wt. % 1-propanol.
 4. The method of claim 1, wherein the step ofcontacting a gaseous material is conducted at a pressure of from about0.5 bar (absolute) to about 10 bar (absolute), and at a temperature offrom about 260° C. to about 340° C.
 5. The method of claim 1, whereinthe step of contacting a gaseous material is conducted at a pressure offrom about 4 bar (absolute) to about 7 bar (absolute), and at atemperature of from about 280° C. to about 320° C.
 6. The method ofclaim 1, wherein the step of contacting the mixture of hydrogen gas anddehydrated glycerol material is conducted at a pressure of from about0.5 bar (absolute) to about 10 bar (absolute), and at a temperature offrom about 150° C. to about 400° C.
 7. The method of claim 1, whereinthe step of contacting the mixture of hydrogen gas and dehydratedglycerol material is conducted at a pressure of from about 4 bar(absolute) to about 7 bar (absolute), and at a temperature of from about250° C. to about 350° C.
 8. The method of claim 1, wherein thedehydration catalyst comprises oxides of tungsten and zirconium.
 9. Themethod of claim 1, wherein the hydrogenation catalyst comprises aplatinum group metal.
 10. The method of claim 1, wherein an amount ofhydrogen in the mixture of hydrogen gas and dehydrated glycerol materialis from about 0.9 to about 10 times the amount of carbon-carbon doublebonds and carbon-oxygen double bonds present in the mixture on a molarbasis.
 11. The method of claim 1, further comprising steps of:separating at least a portion of at least one compound selected from thegroup glycerol, propylene glycol, ethylene glycol, hydroxyacetone,propionaldehyde, acrolein, acetone, acetaldehyde, and formaldehyde fromthe dehydrated glycerol material; and contacting the separated portionwith the heterogeneous dehydration catalyst.
 12. The method of claim 1,wherein glycerol is present at a mole fraction of from about 10% toabout 30%, and water is present at a mole fraction of from about 70% toabout 90% in the gaseous material.
 13. The method of claim 1, whereinthe gaseous material further comprises at least one monohydric alcohol.14. The method of claim 13, wherein the monohydric alcohol is selectedfrom the group consisting of methanol, ethanol, and propanol.
 15. Themethod of claim 13, wherein monohydric alcohols make up from about 0.1wt. % to about 30 wt. % of the gaseous material.
 16. The method of claim13, wherein monohydric alcohols make up from about 0.1 wt. % to about 15wt. % of the gaseous material.
 17. The method of claim 13, whereinmonohydric alcohols make up from about 0.1 wt. % to about 5 wt. % of thegaseous material.
 18. The method of claim 13, wherein monohydricalcohols make up from about 0.1 wt. % to about 2 wt. % of the gaseousmaterial.
 19. The method of claim 13, wherein monohydric alcohols makeup less than about 0.5 wt. % of the gaseous material.
 20. The method ofclaim 1, wherein the gaseous material further comprises at least onefatty acid methyl ester.
 21. The method of claim 20, wherein fatty acidmethyl esters make up from about 0.1 wt. % to about 2 wt. % of thegaseous material.
 22. The method of claim 1, wherein the gaseousmaterial further comprises at least one fatty acid ethyl ester.
 23. Themethod of claim 22, wherein fatty acid ethyl esters make up from about0.1 wt. % to about 2 wt. % of the gaseous material.
 24. The method ofclaim 1, wherein the gaseous material further comprises at least onefatty acid propyl ester.
 25. The method of claim 24, wherein fatty acidpropyl esters make up from about 0.1 wt. % to about 2 wt. % of thegaseous material.
 26. The method of claim 1, wherein the gaseousmaterial contains from about 0.1 wt. % to about 20 wt. % hydrogen. 27.The method of claim 1, wherein the gaseous material further compriseshydrogen at about 0.2% to about 2% (molar).
 28. A method for convertingglycerol to monohydric alcohol, the method comprising: contacting agaseous material comprising glycerol with a heterogeneous dehydrationcatalyst at a temperature and a pressure sufficient to yield a firstreacted material comprising carbon monoxide, water, and one or morecarbonyl-containing molecules; contacting the first reacted materialwith a water-gas shift reaction catalyst at a temperature and a pressuresufficient to yield a second reacted material comprising hydrogen; andcontacting the second reacted material with a heterogeneoushydrogenation catalyst at a temperature and a pressure sufficient toconvert at least a portion of the carbonyl-containing molecules to oneor more monohydric alcohols in a hydrogenated material.
 29. The methodof claim 28, wherein the step of contacting a gaseous mixture occurs ata temperature of from about 250° C. to about 380° C., and at a pressureof from about 1 bar (absolute) to about 10 bar (absolute).
 30. Themethod of claim 28, wherein the step of contacting a gaseous mixtureoccurs at a temperature of from about 280° C. to about 320° C., and apressure of from about 4 bar (absolute) to about 7 bar (absolute). 31.The method of claim 28, wherein the heterogeneous dehydration catalystcomprises oxides of tungsten and oxides of zirconium.
 32. The method ofclaim 28, wherein the step of contacting the first reacted material isconducted at a temperature of from about 220° C. to about 380° C., andat a pressure of from about 1 bar (absolute) to about 10 bar (absolute).33. The method of claim 28, wherein the step of contacting the firstreacted material is conducted at a temperature of from about 270° C. toabout 330° C., and at a pressure of from about 4 (absolute) to about 7bar (absolute).
 34. The method of claim 28, wherein the contacting witha heterogeneous hydrogenation catalyst occurs at a temperature of about150° C. to about 400° C. and the pressure of about 0.5 to about 10 bar(absolute).
 35. The method of claim 28, wherein the step of contactingthe second reacted material is conducted at a temperature of from about250° C. to about 350° C., and at a pressure of from about 4 bar(absolute) to about 7 bar (absolute).
 36. The method of claim 28,further comprising a step of separating an alcohol-rich material and analcohol-depleted material from the hydrogenated material, wherein thealcohol-depleted material comprises predominantly carbon dioxide andhydrogen.
 37. The method of claim 36, wherein the alcohol rich materialcomprises at least 70 wt. % 1-propanol.
 38. The method of claim 36,further comprising a steps of: treating the alcohol-depleted materialvia pressure-swing absorption to remove at least a portion of the carbondioxide present, resulting in a carbon dioxide-rich material and ahydrogen-rich material; and recycling the hydrogen-rich material to thestep of contacting a gaseous material.